Method for transmitting/receiving channel by using guard band in one carrier in wireless communication system, and device therefor

ABSTRACT

A method for receiving a downlink channel by a terminal in a wireless communication system includes: receiving, from a base station, first information related to a guard band in a first resource region located in one carrier; receiving, from the base station, second information related to multiple resource sets, each of which is identified by the guard band in the first resource region on the basis of the first information; and receiving, from the base station, a downlink channel on a resource indicated by the second information to be available for reception of the downlink channel.

TECHNICAL FIELD

The present specification relates to a wireless communication systemand, particularly, to a method for transmitting or receiving a channelby using a guard band in one carrier, and an apparatus therefor.

BACKGROUND ART

After commercialization of 4th generation (4G) communication system, inorder to meet the increasing demand for wireless data traffic, effortsare being made to develop new 5th generation (5G) communication systems.The 5G communication system is called as a beyond 4G networkcommunication system, a post LTE system, or a new radio (NR) system. Inorder to achieve a high data transfer rate, 5G communication systemsinclude systems operated using the millimeter wave (mmWave) band of 6GHz or more, and include a communication system operated using afrequency band of 6 GHz or less in terms of ensuring coverage so thatimplementations in base stations and terminals are under consideration.

A 3rd generation partnership project (3GPP) NR system enhances spectralefficiency of a network and enables a communication provider to providemore data and voice services over a given bandwidth. Accordingly, the3GPP NR system is designed to meet the demands for high-speed data andmedia transmission in addition to supports for large volumes of voice.The advantages of the NR system are to have a higher throughput and alower latency in an identical platform, support for frequency divisionduplex (FDD) and time division duplex (TDD), and a low operation costwith an enhanced end-user environment and a simple architecture.

For more efficient data processing, dynamic TDD of the NR system may usea method for varying the number of orthogonal frequency divisionmultiplexing (OFDM) symbols that may be used in an uplink and downlinkaccording to data traffic directions of cell users. For example, whenthe downlink traffic of the cell is larger than the uplink traffic, thebase station may allocate a plurality of downlink OFDM symbols to a slot(or subframe). Information about the slot configuration should betransmitted to the terminals.

In order to alleviate the path loss of radio waves and increase thetransmission distance of radio waves in the mmWave band, in 5Gcommunication systems, beamforming, massive multiple input/output(massive MIMO), full dimensional MIMO (FD-MIMO), array antenna, analogbeam-forming, hybrid beamforming that combines analog beamforming anddigital beamforming, and large scale antenna technologies are discussed.In addition, for network improvement of the system, in the 5Gcommunication system, technology developments related to evolved smallcells, advanced small cells, cloud radio access network (cloud RAN),ultra-dense network, device to device communication (D2D), vehicle toeverything communication (V2X), wireless backhaul, non-terrestrialnetwork communication (NTN), moving network, cooperative communication,coordinated multi-points (CoMP), interference cancellation, and the likeare being made. In addition, in the 5G system, hybrid FSK and QAMmodulation (FQAM) and sliding window superposition coding (SWSC), whichare advanced coding modulation (ACM) schemes, and filter bankmulti-carrier (FBMC), non-orthogonal multiple access (NOMA), and sparsecode multiple access (SCMA), which are advanced connectivitytechnologies, are being developed.

Meanwhile, in a human-centric connection network where humans generateand consume information, the Internet has evolved into the Internet ofThings (IoT) network, which exchanges information among distributedcomponents such as objects. Internet of Everything (IoE) technology,which combines IoT technology with big data processing technologythrough connection with cloud servers, is also emerging. In order toimplement IoT, technology elements such as sensing technology,wired/wireless communication and network infrastructure, serviceinterface technology, and security technology are required, so that inrecent years, technologies such as sensor network, machine to machine(M2M), and machine type communication (MTC) have been studied forconnection between objects. In the IoT environment, an intelligentinternet technology (IT) service that collects and analyzes datagenerated from connected objects to create new value in human life canbe provided. Through the fusion and mixture of existing informationtechnology (IT) and various industries, IoT can be applied to fieldssuch as smart home, smart building, smart city, smart car or connectedcar, smart grid, healthcare, smart home appliance, and advanced medicalservice.

Accordingly, various attempts have been made to apply the 5Gcommunication system to the IoT network. For example, technologies suchas a sensor network, a machine to machine (M2M), and a machine typecommunication (MTC) are implemented by techniques such as beamforming,MIMO, and array antennas. The application of the cloud RAN as the bigdata processing technology described above is an example of the fusionof 5G technology and IoT technology. Generally, a mobile communicationsystem has been developed to provide voice service while ensuring theuser's activity.

However, the mobile communication system is gradually expanding not onlythe voice but also the data service, and now it has developed to theextent of providing high-speed data service. However, in a mobilecommunication system in which services are currently being provided, amore advanced mobile communication system is required due to a shortagephenomenon of resources and a high-speed service demand of users.

In recent years, with the explosion of mobile traffic due to the spreadof smart devices, it is becoming difficult to cope with the increasingdata usage for providing cellular communication services using only theexisting licensed frequency spectrums or licensed frequency bands.

In such a situation, a method of using an unlicensed frequency spectrumor an unlicensed frequency band (e.g., 2.4 GHz band, 5 GHz band, or thelike) for providing cellular communication services is being discussedas a solution to the problem of lack of spectrum.

Unlike in licensed bands in which telecommunications carriers secureexclusive use rights through procedures such as auctions, in unlicensedbands, multiple communication devices may be used simultaneously withoutrestrictions on the condition that only a certain level of adjacent bandprotection regulations are observed. For this reason, when an unlicensedband is used for cellular communication service, it is difficult toguarantee the communication quality to the level provided in thelicensed band, and it is likely that interference with existing wirelesscommunication devices (e.g., wireless LAN devices) using the unlicensedband occurs.

In order to use LTE and NR technologies in unlicensed bands, research oncoexistence with existing devices for unlicensed bands and efficientsharing of wireless channels with other wireless communication devicesis to be conducted in advance. That is, it is required to develop arobust coexistence mechanism (RCM) such that devices using LTE and NRtechnologies in the unlicensed band do not affect the existing devicesfor unlicensed bands.

DETAILED DESCRIPTION OF THE INVENTION Technical Problem

It is an aspect of the present specification to provide a method fortransmitting or receiving a channel by using a guard band in one carrierin a wireless communication system, and an apparatus therefor.

Technical Solution

The present specification provides a method for receiving a downlinkchannel in a wireless communication system.

Specifically, a method performed by a terminal may include theoperations of: receiving first information related to a guard band in afirst resource region located in one carrier from a base station;receiving second information related to multiple resource sets, each ofwhich is identified by the guard band in the first resource region,based on the first information, from the base station; and receiving,from the base station, a downlink channel on a resource indicated by thesecond information to be available for reception of the downlinkchannel. The multiple resource sets may be configured by resourcesexcept for a resource allocated for the guard band, based on the firstinformation. The second information may be information indicatingwhether each of the multiple resource sets is available for reception ofthe downlink channel.

Furthermore, in connection with the present specification, the methodperformed by a terminal may further include an operation of receiving,from the base station, a physical downlink control channel (PDCCH) on apart of the multiple resource sets. The second information may beincluded in downlink control information (DCI) of the PDCCH.

Furthermore, in connection with the present specification, the methodperformed by a terminal may further include an operation of receiving,from the base station, information relating to a second resource regionthat the terminal monitors to receive the PDCCH.

A terminal for receiving a downlink channel in a wireless communicationsystem may include: a transceiver; a processor; and a memory configuredto store instructions for operations executed by the processor andconnected to the processor. The operations may include: receiving firstinformation related to a guard band in a first resource region locatedin one carrier from a base station; receiving second information relatedto multiple resource sets, each of which is identified by the guard bandin the first resource region, based on the first information, from thebase station; and receiving, from the base station, a downlink channelon a resource indicated by the second information to be available fortransmission of the downlink channel. The multiple resource sets may beconfigured by resources except for a resource allocated for the guardband, based on the first information. The second information may beinformation indicating whether each of the multiple resource sets isavailable for reception of the downlink channel.

In addition, the operations may further include: receiving, from thebase station, a physical downlink control channel (PDCCH) on a part ofthe multiple resource sets. The second information may be included indownlink control information (DCI) of the PDCCH.

In addition, the operations may further include: receiving, from thebase station, information relating to a second resource region that theterminal monitors to receive the PDCCH.

Furthermore, in connection with the present specification, the DCI maybe group-common DCI.

Furthermore, in connection with the present specification, the secondresource region may correspond to a part of the multiple resource sets,and the second resource region may include a resource on which the PDCCHis received.

Furthermore, in connection with the present specification, the secondresource region may be a resource to which a control resource set(CORESET) is allocated.

Furthermore, in connection with the present specification, the secondinformation may indicate whether each of the multiple resource sets isavailable for transmission of the downlink channel, in a bitmap type.

Furthermore, in connection with the present specification, the downlinkchannel may be at least one of a physical downlink control channel(PDCCH) and a physical downlink shared channel (PDSCH).

Furthermore, in connection with the present specification, the firstinformation and information relating to a second resource region may betransmitted through higher layer signaling.

Furthermore, in connection with the present specification, a method fortransmitting a downlink channel by a base station in a wirelesscommunication system may include the operations of: transmitting firstinformation related to a guard band in a first resource region locatedin one carrier to a terminal; transmitting second information related tomultiple resource sets, each of which is identified by the guard band inthe first resource region, based on the first information, to theterminal; and transmitting, to the terminal, a downlink channel on aresource indicated by the second information to be available fortransmission of the downlink channel. The multiple resource sets may beconfigured by resources except for a resource allocated for the guardband, based on the first information. The second information may beinformation indicating whether each of the multiple resource sets isavailable for transmission of the downlink channel.

Furthermore, in connection with the present specification, the secondinformation may indicate whether each of the multiple resource sets isavailable for transmission of the downlink channel, in a bitmap type.

Advantageous Effects

The present specification is advantageous in that efficient channeltransmission is made possible by providing a method for configuringresources for uplink channel and downlink channel transmission when aguard band exists inside a single carrier.

Advantageous effects obtainable in the present specification are notlimited to the above-mentioned advantageous effects, and otheradvantageous effects not mentioned herein may be clearly understood by aperson skilled in the art to which the present disclosure pertains fromthe following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a wireless frame structure used in awireless communication system;

FIG. 2 illustrates an example of a downlink (DL)/uplink (UL) slotstructure in a wireless communication system;

FIG. 3 is a diagram for explaining a physical channel used in a 3GPPsystem and a typical signal transmission method using the physicalchannel;

FIG. 4 illustrates an SS/PBCH block for initial cell access in a 3GPP NRsystem;

FIG. 5 illustrates a procedure for transmitting control information anda control channel in a 3GPP NR system;

FIG. 6 illustrates a control resource set (CORESET) in which a physicaldownlink control channel (PUCCH) may be transmitted in a 3GPP NR system;

FIG. 7 illustrates a method for configuring a PDCCH search space in a3GPP NR system;

FIG. 8 is a conceptual diagram illustrating carrier aggregation;

FIG. 9 is a diagram for explaining signal carrier communication andmultiple carrier communication;

FIG. 10 is a diagram showing an example in which a cross carrierscheduling technique is applied;

FIG. 11 illustrates an example of a scenario of placing a terminal and abase station in an LAA service environment;

FIG. 12 illustrates an example of a conventional communication schemeoperated in an unlicensed band;

FIGS. 13 and 14 illustrate an example of a listen-before-talk (LBT)process for DL transmission;

FIG. 15 illustrates an example of a DL transmission in an unlicensedband;

FIG. 16 illustrates an example of a method for adjusting a contentionwindow size (CWS) at the time of channel access in an unlicensed band;

FIG. 17 illustrates an example of a method for configuring, forterminals, a bandwidth part (BWP) having a bandwidth equal to or smallerthan the bandwidth of a carrier (or a cell) in a 3GPP NR system;

FIG. 18 illustrates an example in which, when multiple BWPs are assignedto a terminal, at least one CORESET in each of the BWPs is configured orassigned to the terminal;

FIG. 19 shows an operation of, when a base station according to anembodiment of the present disclosure configures a BWP including one ormore basic bandwidths, transmitting a PDCCH in a CORESET configured ineach of the basic bandwidths, on the basis of the priorities of thebasic bandwidths, and transmitting a PDSCH in the BWP;

FIG. 20 shows an operation in which, when a BWP is configured to includeone or more basic bandwidths according to an embodiment of the presentdisclosure, a base station transmits a PDCCH in a CORESET configured ineach of designated basic bandwidths, according to the prioritiesthereof, and transmits a PDSCH in the BWP;

FIG. 21 shows an operation in which, when a BWP is configured to includeone or more basic bandwidths according to an embodiment of the presentdisclosure, one or more basic bandwidths in which a base station cantransmit a PDCCH are designated, and the base station transmits a PDCCHin a CORESET configured in each of the designated basic bandwidths,according to the designated basic bandwidths, and transmits a PDSCH inthe BWP;

FIG. 22 is a diagram illustrating in-carrier guard bands and carrierguard bands in a BWP configured by one or more LBT subbands in awideband carrier;

FIG. 23 illustrates one embodiment of the number of physical resourceblocks (RBs) which can be continuously used when a BWP having abandwidth of 20 MHz, 40 MHz, or 80 MHz is used;

FIG. 24 illustrates one embodiment of the number of physical resourceRBs which can be continuously used as an in-carrier guard band when aBWP having a bandwidth of 20 MHz, 40 MHz, or 80 MHz is used, andillustrates one embodiment of the number of physical resource RBs whichcan be used for each LBT subband according to a BWP having a bandwidthof 20 MHz, 40 MHz, or 80 MHz;

FIG. 25 illustrates a block diagram illustrating a configuration of aterminal and a base station according to an embodiment of the presentdisclosure; and

FIG. 26 is a flowchart of a method for receiving a downlink channel by aterminal according to an embodiment of the present disclosure.

MODE FOR CARRYING OUT THE INVENTION

Terms used in the specification adopt general terms which are currentlywidely used as possible by considering functions in the presentinvention, but the terms may be changed depending on an intention ofthose skilled in the art, customs, and emergence of new technology.Further, in a specific case, there is a term arbitrarily selected by anapplicant and in this case, a meaning thereof will be described in acorresponding description part of the invention. Accordingly, it intendsto be revealed that a term used in the specification should be analyzedbased on not just a name of the term but a substantial meaning of theterm and contents throughout the specification.

Throughout this specification and the claims that follow, when it isdescribed that an element is “connected” to another element, the elementmay be “directly connected” to the other element or “electricallyconnected” to the other element through a third element. Further, unlessexplicitly described to the contrary, the word “comprise” will beunderstood to imply the inclusion of stated elements but not theexclusion of any other elements unless otherwise stated. Moreover,limitations such as “more than or equal to” or “less than or equal to”based on a specific threshold may be appropriately substituted with“more than” or “less than”, respectively, in some exemplary embodiments.

The following technology may be used in various wireless access systems,such as code division multiple access (CDMA), frequency divisionmultiple access (FDMA), time division multiple access (TDMA), orthogonalfrequency division multiple access (OFDMA), single carrier-FDMA(SC-FDMA), and the like. The CDMA may be implemented by a wirelesstechnology such as universal terrestrial radio access (UTRA) orCDMA2000. The TDMA may be implemented by a wireless technology such asglobal system for mobile communications (GSM)/general packet radioservice (GPRS)/enhanced data rates for GSM evolution (EDGE). The OFDMAmay be implemented by a wireless technology such as IEEE 802.11(Wi-Fi),IEEE 802.16(WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), and the like.The UTRA is a part of a universal mobile telecommunication system(UMTS). 3rd generation partnership project (3GPP) long term evolution(LTE) is a part of an evolved UMTS (E-UMTS) using evolved-UMTSterrestrial radio access (E-UTRA) and LTE-advanced (A) is an evolvedversion of the 3GPP LTE. 3GPP new radio (NR) is a system designedseparately from LTE/LTE-A, and is a system for supporting enhancedmobile broadband (eMBB), ultra-reliable and low latency communication(URLLC), and massive machine type communication (mMTC) services, whichare requirements of IMT-2020. For the clear description, 3GPP NR ismainly described, but the technical idea of the present invention is notlimited thereto.

Unless otherwise specified herein, the base station may include a nextgeneration node B (gNB) defined in 3GPP NR. Furthermore, unlessotherwise specified, a terminal may include a user equipment (UE).Hereinafter, in order to help the understanding of the description, eachcontent is described separately by the embodiments, but each embodimentmay be used in combination with each other. In the presentspecification, the configuration of the UE may indicate a configurationby the base station. In more detail, the base station may configure avalue of a parameter used in an operation of the UE or a wirelesscommunication system by transmitting a channel or a signal to the UE.

FIG. 1 illustrates an example of a wireless frame structure used in awireless communication system.

Referring to FIG. 1 , the wireless frame (or radio frame) used in the3GPP NR system may have a length of 10 ms (Δf_(max)N_(f)/100)*T_(c)). Inaddition, the wireless frame includes 10 subframes (SFs) having equalsizes. Herein, Δf_(max)=480*10³ Hz, N_(f)=4096,T_(c)=1/(Δf_(ref)*N_(f,ref)), Δf_(ref)=15*10³ Hz, and N_(f,ref)=2048.Numbers from 0 to 9 may be respectively allocated to 10 subframes withinone wireless frame. Each subframe has a length of 1 ms and may includeone or more slots according to a subcarrier spacing. More specifically,in the 3GPP NR system, the subcarrier spacing that may be used is15*2^(μ) kHz, and p can have a value of μ=0, 1, 2, 3, 4 as subcarrierspacing configuration. That is, 15 kHz, 30 kHz, 60 kHz, 120 kHz and 240kHz may be used for subcarrier spacing. One subframe having a length of1 ms may include 2^(μ) slots. In this case, the length of each slot is2^(−μ) ms. Numbers from 0 to 2^(μ)-1 may be respectively allocated to2^(μ) slots within one wireless frame. In addition, numbers from 0 to10*2^(μ)-1 may be respectively allocated to slots within one subframe.The time resource may be distinguished by at least one of a wirelessframe number (also referred to as a wireless frame index), a subframenumber (also referred to as a subframe index), and a slot number (or aslot index).

FIG. 2 illustrates an example of a downlink (DL)/uplink (UL) slotstructure in a wireless communication system. In particular, FIG. 2shows the structure of the resource grid of the 3GPP NR system.

There is one resource grid per antenna port. Referring to FIG. 2 , aslot includes a plurality of orthogonal frequency division multiplexing(OFDM) symbols in a time domain and includes a plurality of resourceblocks (RBs) in a frequency domain. An OFDM symbol also means one symbolsection. Unless otherwise specified, OFDM symbols may be referred tosimply as symbols. One RB includes 12 consecutive subcarriers in thefrequency domain. Referring to FIG. 2 , a signal transmitted from eachslot may be represented by a resource grid including N^(size,μ)_(grid,x)*N^(RB) _(sc) subcarriers, and N^(slot) _(symb) OFDM symbols.Here, x=DL when the signal is a DL signal, and x=UL when the signal isan UL signal. N^(size,μ) _(grid,x) represents the number of resourceblocks (RBs) according to the subcarrier spacing constituent μ (x is DLor UL), and N^(slot) _(symb) represents the number of OFDM symbols in aslot. N^(RB) _(sc) is the number of subcarriers constituting one RB andN^(RB) _(sc)=12. An OFDM symbol may be referred to as a cyclic shiftOFDM (CP-OFDM) symbol or a discrete Fourier transform spread OFDM(DFT-s-OFDM) symbol according to a multiple access scheme.

The number of OFDM symbols included in one slot may vary according tothe length of a cyclic prefix (CP). For example, in the case of a normalCP, one slot includes 14 OFDM symbols, but in the case of an extendedCP, one slot may include 12 OFDM symbols. In a specific embodiment, theextended CP can only be used at 60 kHz subcarrier spacing. In FIG. 2 ,for convenience of description, one slot is configured with 14 OFDMsymbols by way of example, but embodiments of the present disclosure maybe applied in a similar manner to a slot having a different number ofOFDM symbols. Referring to FIG. 2 , each OFDM symbol includes N^(size,μ)_(grid,x)*N^(RB) _(sc) subcarriers in the frequency domain. The type ofsubcarrier may be divided into a data subcarrier for data transmission,a reference signal subcarrier for transmission of a reference signal,and a guard band. The carrier frequency is also referred to as thecenter frequency (fc).

One RB may be defined by N^(RB) _(sc) (e. g., 12) consecutivesubcarriers in the frequency domain. For reference, a resourceconfigured with one OFDM symbol and one subcarrier may be referred to asa resource element (RE) or a tone. Therefore, one RB can be configuredwith N^(slot) _(symb)*N^(RB) _(sc) resource elements. Each resourceelement in the resource grid can be uniquely defined by a pair ofindexes (k, 1) in one slot. k may be an index assigned from 0 toN^(size,μ) _(grid, x)*N^(RB) _(sc)−1 in the frequency domain, and 1 maybe an index assigned from 0 to N^(slot) _(symb)−1 in the time domain.

In order for the UE to receive a signal from the base station or totransmit a signal to the base station, the time/frequency of the UE maybe synchronized with the time/frequency of the base station. This isbecause when the base station and the UE are synchronized, the UE candetermine the time and frequency parameters necessary for demodulatingthe DL signal and transmitting the UL signal at the correct time.

Each symbol of a radio frame used in a time division duplex (TDD) or anunpaired spectrum may be configured with at least one of a DL symbol, anUL symbol, and a flexible symbol. A radio frame used as a DL carrier ina frequency division duplex (FDD) or a paired spectrum may be configuredwith a DL symbol or a flexible symbol, and a radio frame used as a ULcarrier may be configured with a UL symbol or a flexible symbol. In theDL symbol, DL transmission is possible, but UL transmission isimpossible. In the UL symbol, UL transmission is possible, but DLtransmission is impossible. The flexible symbol may be determined to beused as a DL or an UL according to a signal.

Information on the type of each symbol, i.e., information representingany one of DL symbols, UL symbols, and flexible symbols, may beconfigured with a cell-specific or common radio resource control (RRC)signal. In addition, information on the type of each symbol mayadditionally be configured with a UE-specific or dedicated RRC signal.The base station informs, by using cell-specific RRC signals, i) theperiod of cell-specific slot configuration, ii) the number of slots withonly DL symbols from the beginning of the period of cell-specific slotconfiguration, iii) the number of DL symbols from the first symbol ofthe slot immediately following the slot with only DL symbols, iv) thenumber of slots with only UL symbols from the end of the period of cellspecific slot configuration, and v) the number of UL symbols from thelast symbol of the slot immediately before the slot with only the ULsymbol. Here, symbols not configured with any one of a UL symbol and aDL symbol are flexible symbols.

When the information on the symbol type is configured with theUE-specific RRC signal, the base station may signal whether the flexiblesymbol is a DL symbol or an UL symbol in the cell-specific RRC signal.In this case, the UE-specific RRC signal can not change a DL symbol or aUL symbol configured with the cell-specific RRC signal into anothersymbol type. The UE-specific RRC signal may signal the number of DLsymbols among the N^(slot) _(symb) symbols of the corresponding slot foreach slot, and the number of UL symbols among the N^(slot) _(symb)symbols of the corresponding slot. In this case, the DL symbol of theslot may be continuously configured with the first symbol to the i-thsymbol of the slot. In addition, the UL symbol of the slot may becontinuously configured with the j-th symbol to the last symbol of theslot (where i<j). In the slot, symbols not configured with any one of aUL symbol and a DL symbol are flexible symbols.

The type of symbol configured with the above RRC signal may be referredto as a semi-static DL/UL configuration. In the semi-static DL/ULconfiguration previously configured with RRC signals, the flexiblesymbol may be indicated as a DL symbol, an UL symbol, or a flexiblesymbol through dynamic slot format information (SFI) transmitted on aphysical DL control channel (PDCCH). In this case, the DL symbol or ULsymbol configured with the RRC signal is not changed to another symboltype. Table 1 exemplifies the dynamic SFI that the base station canindicate to the UE.

TABLE 1 Symbol number in a slot index 0 1 2 3 4 5 6 7 8 9 10 11 12 13  0D D D D D D D D D D D D D D  1 U U U U U U U U U U U U U U  2 X X X X XX X X X X X X X X  3 D D D D D D D D D D D D D X  4 D D D D D D D D D DD D X X  5 D D D D D D D D D D D X X X  6 D D D D D D D D D D X X X X  7D D D D D D D D D X X X X X  8 X X X X X X X X X X X X X U  9 X X X X XX X X X X X X U U 10 X U U U U U U U U U U U U U 11 X X U U U U U U U UU U U U 12 X X X U U U U U U U U U U U 13 X X X X U U U U U U U U U U 14X X X X X U U U U U U U U U 15 X X X X X X U U U U U U U U 16 D X X X XX X X X X X X X X 17 D D X X X X X X X X X X X X 18 D D D X X X X X X XX X X X 19 D X X X X X X X X X X X X U 20 D D X X X X X X X X X X X U 21D D D X X X X X X X X X X U 22 D X X X X X X X X X X X U U 23 D D X X XX X X X X X X U U 24 D D D X X X X X X X X X U U 25 D X X X X X X X X XX U U U 26 D D X X X X X X X X X U U U 27 D D D X X X X X X X X U U U 28D D D D D D D D D D D D X U 29 D D D D D D D D D D D X X U 30 D D D D DD D D D D X X X U 31 D D D D D D D D D D D X U U 32 D D D D D D D D D DX X U U 33 D D D D D D D D D X X X U U 34 D X U U U U U U U U U U U U 35D D X U U U U U U U U U U U 36 D D D X U U U U U U U U U U 37 D X X U UU U U U U U U U U 38 D D X X U U U U U U U U U U 39 D D D X X U U U U UU U U U 40 D X X X U U U U U U U U U U 41 D D X X X U U U U U U U U U 42D D D X X X U U U U U U U U 43 D D D D D D D D D X X X X U 44 D D D D DD X X X X X X U U 45 D D D D D D X X U U U U U U 46 D D D D D X U D D DD D X U 47 D D X U U U U D D X U U U U 48 D X U U U U U D X U U U U U 49D D D D X X U D D D D X X U 50 D D X X U U U D D X X U U U 51 D X X U UU U D X X U U U U 52 D X X X X X U D X X X X X U 53 D D X X X X U D D XX X X U 54 X X X X X X X D D D D D D D 55 D D X X X U U U D D D D D D56~255 Reserved

In Table 1, D denotes a DL symbol, U denotes a UL symbol, and X denotesa flexible symbol. As shown in Table 1, up to two DL/UL switching in oneslot may be allowed.

FIG. 3 is a diagram for explaining a physical channel used in a 3GPPsystem (e.g., NR) and a typical signal transmission method using thephysical channel.

If the power of the UE is turned on or the UE camps on a new cell, theUE performs an initial cell search (S101). Specifically, the UE maysynchronize with the BS in the initial cell search. For this, the UE mayreceive a primary synchronization signal (PSS) and a secondarysynchronization signal (SSS) from the base station to synchronize withthe base station, and obtain information such as a cell index.Thereafter, the UE can receive the physical broadcast channel from thebase station and obtain the broadcast information in the cell.

Upon completion of the initial cell search, the UE receives a physicaldownlink shared channel (PDSCH) according to the physical downlinkcontrol channel (PDCCH) and information in the PDCCH, so that the UE canobtain more specific system information than the system informationobtained through the initial cell search (S102). Herein, the systeminformation received by the UE is cell-common system information fornormal operating of the UE in a physical layer in radio resource control(RRC) and is referred to remaining system information, or systeminformation block (SIB) 1 is called.

When the UE initially accesses the base station or does not have radioresources for signal transmission (i.e. the UE at RRC IDLE mode), the UEmay perform a random access procedure on the base station (operationsS103 to S106). First, the UE can transmit a preamble through a physicalrandom access channel (PRACH) (S103) and receive a response message forthe preamble from the base station through the PDCCH and thecorresponding PDSCH (S104). When a valid random access response messageis received by the UE, the UE transmits data including the identifier ofthe UE and the like to the base station through a physical uplink sharedchannel (PUSCH) indicated by the UL grant transmitted through the PDCCHfrom the base station (S105). Next, the UE waits for reception of thePDCCH as an indication of the base station for collision resolution. Ifthe UE successfully receives the PDCCH through the identifier of the UE(S106), the random access process is terminated. The UE may obtainUE-specific system information for normal operating of the UE in thephysical layer in RRC layer during a random access process. When the UEobtain the UE-specific system information, the UE enter RRC connectingmode (RRC_CONNECTED mode).

The RRC layer is used for generating or managing message for controllingconnection between the UE and radio access network (RAN). In moredetail, the base station and the UE, in the RRC layer, may performbroadcasting cell system information required by every UE in the cell,managing mobility and handover, measurement report of the UE, storagemanagement including UE capability management and device management. Ingeneral, the RRC signal is not changed and maintained quite longinterval since a period of an update of a signal delivered in the RRClayer is longer than a transmission time interval (TTI) in physicallayer.

After the above-described procedure, the UE receives PDCCH/PDSCH (S107)and transmits a physical uplink shared channel (PUSCH)/physical uplinkcontrol channel (PUCCH) (S108) as a general UL/DL signal transmissionprocedure. In particular, the UE may receive downlink controlinformation (DCI) through the PDCCH. The DCI may include controlinformation such as resource allocation information for the UE. Also,the format of the DCI may vary depending on the intended use. The uplinkcontrol information (UCI) that the UE transmits to the base stationthrough UL includes a DL/UL ACK/NACK signal, a channel quality indicator(CQI), a precoding matrix index (PMI), a rank indicator (RI), and thelike. Here, the CQI, PMI, and RI may be included in channel stateinformation (CSI). In the 3GPP NR system, the UE may transmit controlinformation such as HARQ-ACK and CSI described above through the PUSCHand/or PUCCH.

FIG. 4 illustrates an SS/PBCH block for initial cell access in a 3GPP NRsystem.

When the power is turned on or wanting to access a new cell, the UE mayobtain time and frequency synchronization with the cell and perform aninitial cell search procedure. The UE may detect a physical cellidentity N^(cell) _(ID) of the cell during a cell search procedure. Forthis, the UE may receive a synchronization signal, for example, aprimary synchronization signal (PSS) and a secondary synchronizationsignal (SSS), from a base station, and synchronize with the basestation. In this case, the UE can obtain information such as a cellidentity (ID).

Referring to FIG. 4(a), a synchronization signal (SS) will be describedin more detail. The synchronization signal can be classified into PSSand SSS. The PSS may be used to obtain time domain synchronizationand/or frequency domain synchronization, such as OFDM symbolsynchronization and slot synchronization. The SSS can be used to obtainframe synchronization and cell group ID. Referring to FIG. 4(a) andTable 2, the SS/PBCH block can be configured with consecutive 20 RBs(=240 subcarriers) in the frequency axis, and can be configured withconsecutive 4 OFDM symbols in the time axis. In this case, in theSS/PBCH block, the PSS is transmitted in the first OFDM symbol and theSSS is transmitted in the third OFDM symbol through the 56th to 182thsubcarriers. Here, the lowest subcarrier index of the SS/PBCH block isnumbered from 0. In the first OFDM symbol in which the PSS istransmitted, the base station does not transmit a signal through theremaining subcarriers, i.e., 0th to 55th and 183th to 239th subcarriers.In addition, in the third OFDM symbol in which the SSS is transmitted,the base station does not transmit a signal through 48th to 55th and183th to 191th subcarriers. The base station transmits a physicalbroadcast channel (PBCH) through the remaining RE except for the abovesignal in the SS/PBCH block.

TABLE 2 OFDM symbol number l Subcarrier number k Channel relative to thestart relative to the start or signal of an SS/PBCH block of an SS/PBCHblock PSS 0 56, 57, . . . , 182 SSS 2 56, 57, . . . , 182 Set to 0 0 0,1, . . . , 55, 183, 184, . . . , 239 2 48, 49, . . . , 55, 183, 184, . .. , 191 PBCH 1, 3 0, 1, . . . , 239 2 0, 1, . . . , 47, 192, 193, . . ., 239 DM-RS for 1, 3 0 + v, 4 + v, 8 + PBCH v, . . . , 236 + v 2 0 + v,4 + v, 8 + v, . . . , 44 + v 192 + v, 196 + v, . . . , 236 + v

The SS allows a total of 1008 unique physical layer cell IDs to begrouped into 336 physical-layer cell-identifier groups, each groupincluding three unique identifiers, through a combination of three PSSsand SSSs, specifically, such that each physical layer cell ID is to beonly a part of one physical-layer cell-identifier group. Therefore, thephysical layer cell ID N^(cell) _(ID)=3N⁽¹⁾ _(ID)+N⁽²⁾ _(ID) can beuniquely defined by the index N⁽¹⁾ _(ID) ranging from 0 to 335indicating a physical-layer cell-identifier group and the index N⁽²⁾_(ID) ranging from 0 to 2 indicating a physical-layer identifier in thephysical-layer cell-identifier group. The UE may detect the PSS andidentify one of the three unique physical-layer identifiers. Inaddition, the UE can detect the SSS and identify one of the 336 physicallayer cell IDs associated with the physical-layer identifier. In thiscase, the sequence d_(PSS)(n) of the PSS is as follows.

d _(PSS)(n)=1−2x(m)

m=(n+43N ⁽²⁾ _(ID))mod 127

0≤n<127

Here, x(i+7)=(x(i+4)+x(i))mod2 and is given as,

[x(6)x(5)x(4)x(3)x(2)x(1)x(0)]=[11 10 11 0]

Further, the sequence d_(SSS)(n) of the SSS is as follows.

d_(SSS)(n) = [1 − 2x₀((n + m₀)mod127)][1 − 2x₁((n + m₁)mod127)]$m_{0} = {{15\left\lfloor \frac{N_{ID}^{(1)}}{112} \right\rfloor} + {5N_{ID}^{(2)}}}$m₁ = N_(ID)⁽¹⁾mod112 0 ≤ n < 127 x₀(i + 7) = (x₀(i + 4) + x₀(i))mod2

Here, x₁(i+7)=(x₁(i+1)+x₁(i))mod2 and is given as,

[x ₀(6)x ₀(5)x ₀(4)x ₀(3)x ₀(2)x ₀(1)x ₀(0)]=[00 00 00 1]

[x ₁(6)x ₁(5)x ₁(4)x ₁(3)x ₁(2)x ₁(1)x ₁(0)]=[00 00 00 1]

A radio frame with a 10 ms length may be divided into two half frameswith a 5 ms length. Referring to FIG. 4B, a description will be made ofa slot in which SS/PBCH blocks are transmitted in each half frame. Aslot in which the SS/PBCH block is transmitted may be any one of thecases A, B, C, D, and E. In the case A, the subcarrier spacing is 15 kHzand the starting time point of the SS/PBCH block is the ({2, 8}+14*n)-thsymbol. In this case, n=0 or 1 at a carrier frequency of 3 GHz or less.In addition, it may be n=0, 1, 2, 3 at carrier frequencies above 3 GHzand below 6 GHz. In the case B, the subcarrier spacing is 30 kHz and thestarting time point of the SS/PBCH block is {4, 8, 16, 20}+28*n. In thiscase, n=0 at a carrier frequency of 3 GHz or less. In addition, it maybe n=0, 1 at carrier frequencies above 3 GHz and below 6 GHz. In thecase C, the subcarrier spacing is 30 kHz and the starting time point ofthe SS/PBCH block is the ({2, 8}+14*n)-th symbol. In this case, n=0 or 1at a carrier frequency of 3 GHz or less. In addition, it may be n=0, 1,2, 3 at carrier frequencies above 3 GHz and below 6 GHz. In the case D,the subcarrier spacing is 120 kHz and the starting time point of theSS/PBCH block is the ({4, 8, 16, 20}+28*n)-th symbol. In this case, at acarrier frequency of 6 GHz or more, n=0, 1, 2, 3, 5, 6, 7, 8, 10, 11,12, 13, 15, 16, 17, 18. In the case E, the subcarrier spacing is 240 kHzand the starting time point of the SS/PBCH block is the ({8, 12, 16, 20,32, 36, 40, 44}+56*n)-th symbol. In this case, at a carrier frequency of6 GHz or more, n=0, 1, 2, 3, 5, 6, 7, 8.

FIG. 5 illustrates a procedure for transmitting control information anda control channel in a 3GPP NR system. Referring to FIG. 5(a), the basestation may add a cyclic redundancy check (CRC) masked (e.g., an XORoperation) with a radio network temporary identifier (RNTI) to controlinformation (e.g., downlink control information (DCI)) (S202). The basestation may scramble the CRC with an RNTI value determined according tothe purpose/target of each control information. The common RNTI used byone or more UEs can include at least one of a system information RNTI(SI-RNTI), a paging RNTI (P-RNTI), a random access RNTI (RA-RNTI), and atransmit power control RNTI (TPC-RNTI). In addition, the UE-specificRNTI may include at least one of a cell temporary RNTI (C-RNTI), and theCS-RNTI. Thereafter, the base station may perform rate-matching (S206)according to the amount of resource(s) used for PDCCH transmission afterperforming channel encoding (e.g., polar coding) (S204). Thereafter, thebase station may multiplex the DCI(s) based on the control channelelement (CCE) based PDCCH structure (S208). In addition, the basestation may apply an additional process (S210) such as scrambling,modulation (e.g., QPSK), interleaving, and the like to the multiplexedDCI(s), and then map the DCI(s) to the resource to be transmitted. TheCCE is a basic resource unit for the PDCCH, and one CCE may include aplurality (e.g., six) of resource element groups (REGs). One REG may beconfigured with a plurality (e.g., 12) of REs. The number of CCEs usedfor one PDCCH may be defined as an aggregation level. In the 3GPP NRsystem, an aggregation level of 1, 2, 4, 8, or 16 may be used. FIG. 5(b)is a diagram related to a CCE aggregation level and the multiplexing ofa PDCCH and illustrates the type of a CCE aggregation level used for onePDCCH and CCE(s) transmitted in the control area according thereto.

FIG. 6 illustrates a control resource set (CORESET) in which a physicaldownlink control channel (PUCCH) may be transmitted in a 3GPP NR system.

The CORESET is a time-frequency resource in which PDCCH, that is, acontrol signal for the UE, is transmitted. In addition, a search spaceto be described later may be mapped to one CORESET. Therefore, the UEmay monitor the time-frequency domain designated as CORESET instead ofmonitoring all frequency bands for PDCCH reception, and decode the PDCCHmapped to CORESET. The base station may configure one or more CORESETsfor each cell to the UE. The CORESET may be configured with up to threeconsecutive symbols on the time axis. In addition, the CORESET may beconfigured in units of six consecutive PRBs on the frequency axis. Inthe embodiment of FIG. 5 , CORESET #1 is configured with consecutivePRBs, and CORESET #2 and CORESET #3 are configured with discontinuousPRBs. The CORESET can be located in any symbol in the slot. For example,in the embodiment of FIG. 5 , CORESET #1 starts at the first symbol ofthe slot, CORESET #2 starts at the fifth symbol of the slot, and CORESET#9 starts at the ninth symbol of the slot.

FIG. 7 illustrates a method for setting a PUCCH search space in a 3GPPNR system.

In order to transmit the PDCCH to the UE, each CORESET may have at leastone search space. In the embodiment of the present disclosure, thesearch space is a set of all time-frequency resources (hereinafter,PDCCH candidates) through which the PDCCH of the UE is capable of beingtransmitted. The search space may include a common search space that theUE of the 3GPP NR is required to commonly search and a UE-specific or aUE-specific search space that a specific UE is required to search. Inthe common search space, UE may monitor the PDCCH that is set so thatall UEs in the cell belonging to the same base station commonly search.In addition, the UE-specific search space may be set for each UE so thatUEs monitor the PDCCH allocated to each UE at different search spaceposition according to the UE. In the case of the UE-specific searchspace, the search space between the UEs may be partially overlapped andallocated due to the limited control area in which the PDCCH may beallocated. Monitoring the PDCCH includes blind decoding for PDCCHcandidates in the search space. When the blind decoding is successful,it may be expressed that the PDCCH is (successfully) detected/receivedand when the blind decoding fails, it may be expressed that the PDCCH isnot detected/not received, or is not successfully detected/received.

For convenience of explanation, a PDCCH scrambled with a group common(GC) RNTI previously known to one or more UEs so as to transmit DLcontrol information to the one or more UEs is referred to as a groupcommon (GC) PDCCH or a common PDCCH. In addition, a PDCCH scrambled witha specific-terminal RNTI that a specific UE already knows so as totransmit UL scheduling information or DL scheduling information to thespecific UE is referred to as a specific-UE PDCCH. The common PDCCH maybe included in a common search space, and the UE-specific PDCCH may beincluded in a common search space or a UE-specific PDCCH.

The base station may signal each UE or UE group through a PDCCH aboutinformation (i.e., DL Grant) related to resource allocation of a pagingchannel (PCH) and a downlink-shared channel (DL-SCH) that are atransmission channel or information (i.e., UL grant) related to resourceallocation of a uplink-shared channel (UL-SCH) and a hybrid automaticrepeat request (HARD). The base station may transmit the PCH transportblock and the DL-SCH transport block through the PDSCH. The base stationmay transmit data excluding specific control information or specificservice data through the PDSCH. In addition, the UE may receive dataexcluding specific control information or specific service data throughthe PDSCH.

The base station may include, in the PDCCH, information on to which UE(one or a plurality of UEs) PDSCH data is transmitted and how the PDSCHdata is to be received and decoded by the corresponding UE, and transmitthe PDCCH. For example, it is assumed that the DCI transmitted on aspecific PDCCH is CRC masked with an RNTI of “A”, and the DCI indicatesthat PDSCH is allocated to a radio resource (e.g., frequency location)of “B” and indicates transmission format information (e.g., transportblock size, modulation scheme, coding information, etc.) of “C”. The UEmonitors the PDCCH using the RNTI information that the UE has. In thiscase, if there is a UE which performs blind decoding the PDCCH using the“A” RNTI, the UE receives the PDCCH, and receives the PDSCH indicated by“B” and “C” through the received PDCCH information.

Table 3 shows an embodiment of a physical uplink control channel (PUCCH)used in a wireless communication system.

TABLE 3 PUCCH format Length in OFDM symbols Number of bits 0 1-2  ≤2 14-14 ≤2 2 1-2  >2 3 4-14 >2 4 4-14 >2

The PUCCH may be used to transmit the following UL control information(UCI).

-   -   Scheduling Request (SR): Information used for requesting a UL        UL-SCH resource.    -   HARQ-ACK: A Response to PDCCH (indicating DL SPS release) and/or        a response to DL transport block (TB) on PDSCH. HARQ-ACK        indicates whether information successfully transmitted on the        PDCCH or PDSCH is received. The HARQ-ACK response includes        positive ACK (simply ACK), negative ACK (hereinafter NACK),        Discontinuous Transmission (DTX), or NACK/DTX. Here, the term        HARQ-ACK is used mixed with HARQ-ACK/NACK and ACK/NACK. In        general, ACK may be represented by bit value 1 and NACK may be        represented by bit value 0.    -   Channel State Information (CSI): Feedback information on the DL        channel. The UE generates it based on the CSI-Reference Signal        (RS) transmitted by the base station. Multiple Input Multiple        Output (MIMO)-related feedback information includes a Rank        Indicator (RI) and a Precoding Matrix Indicator (PMI). CSI can        be divided into CSI part 1 and CSI part 2 according to the        information indicated by CSI.

In the 3GPP NR system, five PUCCH formats may be used to support variousservice scenarios, various channel environments, and frame structures.

PUCCH format 0 is a format capable of delivering 1-bit or 2-bit HARQ-ACKinformation or SR. PUCCH format 0 can be transmitted through one or twoOFDM symbols on the time axis and one PRB on the frequency axis. WhenPUCCH format 0 is transmitted in two OFDM symbols, the same sequence onthe two symbols may be transmitted through different RBs. In this case,the sequence may be a sequence cyclic shifted (CS) from a base sequenceused in PUCCH format 0. Through this, the UE may obtain a frequencydiversity gain. In more detail, the UE may determine a cyclic shift (CS)value m_(cs) according to M_(bit) bit UCI (M_(bit)=1 or 2). In addition,the base sequence having the length of 12 may be transmitted by mappinga cyclic shifted sequence based on a predetermined CS value m_(cs) toone OFDM symbol and 12 REs of one RB. When the number of cyclic shiftsavailable to the UE is 12 and M_(bit)=1, 1 bit UCI 0 and 1 may be mappedto two cyclic shifted sequences having a difference of 6 in the cyclicshift value, respectively. In addition, when M_(bit)=2, 2 bit UCI 00,01, 11, and 10 may be mapped to four cyclic shifted sequences having adifference of 3 in cyclic shift values, respectively.

PUCCH format 1 may deliver 1-bit or 2-bit HARQ-ACK information or SR.PUCCH format 1 may be transmitted through consecutive OFDM symbols onthe time axis and one PRB on the frequency axis. Here, the number ofOFDM symbols occupied by PUCCH format 1 may be one of 4 to 14. Morespecifically, UCI, which is M_(bit)=1, may be BPSK-modulated. The UE maymodulate UCI, which is M_(bit)=2, with quadrature phase shift keying(QPSK). A signal is obtained by multiplying a modulated complex valuedsymbol d(0) by a sequence of length 12. In this case, the sequence maybe a base sequence used for PUCCH format 0. The UE spreads theeven-numbered OFDM symbols to which PUCCH format 1 is allocated throughthe time axis orthogonal cover code (OCC) to transmit the obtainedsignal. PUCCH format 1 determines the maximum number of different UEsmultiplexed in the one RB according to the length of the OCC to be used.A demodulation reference signal (DMRS) may be spread with OCC and mappedto the odd-numbered OFDM symbols of PUCCH format 1.

PUCCH format 2 may deliver UCI exceeding 2 bits. PUCCH format 2 may betransmitted through one or two OFDM symbols on the time axis and one ora plurality of RBs on the frequency axis. When PUCCH format 2 istransmitted in two 0 OFDM symbols, the sequences which are transmittedin different RBs through the two OFDM symbols may be same each other.Here, the sequence may be a plurality of modulated complex valuedsymbols d(0), . . . , d(M_(symbol)−1). Here, M_(symbol) may beM_(bit)/2. Through this, the UE may obtain a frequency diversity gain.More specifically, M_(bit) bit UCI (M_(bit)>2) is bit-level scrambled,QPSK modulated, and mapped to RB(s) of one or two OFDM symbol(s). Here,the number of RBs may be one of 1 to 16.

PUCCH format 3 or PUCCH format 4 may deliver UCI exceeding 2 bits. PUCCHformat 3 or PUCCH format 4 may be transmitted through consecutive OFDMsymbols on the time axis and one PRB on the frequency axis. The numberof OFDM symbols occupied by PUCCH format 3 or PUCCH format 4 may be oneof 4 to 14. Specifically, the UE modulates M_(bit) bits UCI (Mbit>2)with π/2-Binary Phase Shift Keying (BPSK) or QPSK to generate a complexvalued symbol d(0) to d(M_(symb)−1). Here, when using π/2-BPSK,M_(symb)=M_(bit), and when using QPSK, M_(symb)=M_(bit)/2. The UE maynot apply block-unit spreading to the PUCCH format 3. However, the UEmay apply block-unit spreading to one RB (i.e., 12 subcarriers) usingPreDFT-OCC of a length of 12 such that PUCCH format 4 may have two orfour multiplexing capacities. The UE performs transmit precoding (orDFT-precoding) on the spread signal and maps it to each RE to transmitthe spread signal.

In this case, the number of RBs occupied by PUCCH format 2, PUCCH format3, or PUCCH format 4 may be determined according to the length andmaximum code rate of the UCI transmitted by the UE. When the UE usesPUCCH format 2, the UE may transmit HARQ-ACK information and CSIinformation together through the PUCCH. When the number of RBs that theUE may transmit is greater than the maximum number of RBs that PUCCHformat 2, or PUCCH format 3, or PUCCH format 4 may use, the UE maytransmit only the remaining UCI information without transmitting someUCI information according to the priority of the UCI information.

PUCCH format 1, PUCCH format 3, or PUCCH format 4 may be configuredthrough the RRC signal to indicate frequency hopping in a slot. Whenfrequency hopping is configured, the index of the RB to be frequencyhopped may be configured with an RRC signal. When PUCCH format 1, PUCCHformat 3, or PUCCH format 4 is transmitted through N OFDM symbols on thetime axis, the first hop may have floor (N/2) OFDM symbols and thesecond hop may have ceiling(N/2) OFDM symbols.

PUCCH format 1, PUCCH format 3, or PUCCH format 4 may be configured tobe repeatedly transmitted in a plurality of slots. In this case, thenumber K of slots in which the PUCCH is repeatedly transmitted may beconfigured by the RRC signal. The repeatedly transmitted PUCCHs muststart at an OFDM symbol of the constant position in each slot, and havethe constant length. When one OFDM symbol among OFDM symbols of a slotin which a UE should transmit a PUCCH is indicated as a DL symbol by anRRC signal, the UE may not transmit the PUCCH in a corresponding slotand delay the transmission of the PUCCH to the next slot to transmit thePUCCH.

Meanwhile, in the 3GPP NR system, a UE may performtransmission/reception using a bandwidth equal to or less than thebandwidth of a carrier (or cell). For this, the UE may receive theBandwidth part (BWP) configured with a continuous bandwidth of some ofthe carrier's bandwidth. A UE operating according to TDD or operating inan unpaired spectrum can receive up to four DL/UL BWP pairs in onecarrier (or cell). In addition, the UE may activate one DL/UL BWP pair.A UE operating according to FDD or operating in paired spectrum canreceive up to four DL BWPs on a DL carrier (or cell) and up to four ULBWPs on a UL carrier (or cell). The UE may activate one DL BWP and oneUL BWP for each carrier (or cell). The UE may not perform reception ortransmission in a time-frequency resource other than the activated BWP.The activated BWP may be referred to as an active BWP.

The base station may indicate the activated BWP among the BWPsconfigured by the UE through downlink control information (DCI). The BWPindicated through the DCI is activated and the other configured BWP(s)are deactivated. In a carrier (or cell) operating in TDD, the basestation may include, in the DCI for scheduling PDSCH or PUSCH, abandwidth part indicator (BPI) indicating the BWP to be activated tochange the DL/UL BWP pair of the UE. The UE may receive the DCI forscheduling the PDSCH or PUSCH and may identify the DL/UL BWP pairactivated based on the BPI. For a DL carrier (or cell) operating in anFDD, the base station may include a BPI indicating the BWP to beactivated in the DCI for scheduling PDSCH so as to change the DL BWP ofthe UE. For a UL carrier (or cell) operating in an FDD, the base stationmay include a BPI indicating the BWP to be activated in the DCI forscheduling PUSCH so as to change the UL BWP of the UE.

FIG. 8 is a conceptual diagram illustrating carrier aggregation.

The carrier aggregation is a method in which the UE uses a plurality offrequency blocks or cells (in the logical sense) configured with ULresources (or component carriers) and/or DL resources (or componentcarriers) as one large logical frequency band in order for a wirelesscommunication system to use a wider frequency band. One componentcarrier may also be referred to as a term called a Primary cell (PCell)or a Secondary cell (SCell), or a Primary SCell (PScell). However,hereinafter, for convenience of description, the term “componentcarrier” is used.

Referring to FIG. 8 , as an example of a 3GPP NR system, the entiresystem band may include up to 16 component carriers, and each componentcarrier may have a bandwidth of up to 400 MHz. The component carrier mayinclude one or more physically consecutive subcarriers. Although it isshown in FIG. 8 that each of the component carriers has the samebandwidth, this is merely an example, and each component carrier mayhave a different bandwidth. Also, although each component carrier isshown as being adjacent to each other in the frequency axis, thedrawings are shown in a logical concept, and each component carrier maybe physically adjacent to one another, or may be spaced apart.

Different center frequencies may be used for each component carrier.Also, one common center frequency may be used in physically adjacentcomponent carriers. Assuming that all the component carriers arephysically adjacent in the embodiment of FIG. 8 , center frequency A maybe used in all the component carriers. Further, assuming that therespective component carriers are not physically adjacent to each other,center frequency A and the center frequency B can be used in each of thecomponent carriers.

When the total system band is extended by carrier aggregation, thefrequency band used for communication with each UE can be defined inunits of a component carrier. UE A may use 100 MHz, which is the totalsystem band, and performs communication using all five componentcarriers. UEs B₁˜B₅ can use only a 20 MHz bandwidth and performcommunication using one component carrier. UEs C₁ and C₂ may use a 40MHz bandwidth and perform communication using two component carriers,respectively. The two component carriers may be logically/physicallyadjacent or non-adjacent. UE C₁ represents the case of using twonon-adjacent component carriers, and UE C₂ represents the case of usingtwo adjacent component carriers.

FIG. 9 is a drawing for explaining signal carrier communication andmultiple carrier communication. Particularly, FIG. 9(a) shows a singlecarrier subframe structure and FIG. 9(b) shows a multi-carrier subframestructure.

Referring to FIG. 9(a), in an FDD mode, a general wireless communicationsystem may perform data transmission or reception through one DL bandand one UL band corresponding thereto. In another specific embodiment,in a TDD mode, the wireless communication system may divide a radioframe into a UL time unit and a DL time unit in a time domain, andperform data transmission or reception through a UL/DL time unit.Referring to FIG. 9(b), three 20 MHz component carriers (CCs) can beaggregated into each of UL and DL, so that a bandwidth of 60 MHz can besupported. Each CC may be adjacent or non-adjacent to one another in thefrequency domain. FIG. 9(b) shows a case where the bandwidth of the ULCC and the bandwidth of the DL CC are the same and symmetric, but thebandwidth of each CC can be determined independently. In addition,asymmetric carrier aggregation with different number of UL CCs and DLCCs is possible. A DL/UL CC allocated/configured to a specific UEthrough RRC may be called as a serving DL/UL CC of the specific UE.

The base station may perform communication with the UE by activatingsome or all of the serving CCs of the UE or deactivating some CCs. Thebase station can change the CC to be activated/deactivated, and changethe number of CCs to be activated/deactivated. If the base stationallocates a CC available for the UE as to be cell-specific orUE-specific, at least one of the allocated CCs can be deactivated,unless the CC allocation for the UE is completely reconfigured or the UEis handed over. One CC that is not deactivated by the UE is called as aPrimary CC (PCC) or a primary cell (PCell), and a CC that the basestation can freely activate/deactivate is called as a Secondary CC (SCC)or a secondary cell (SCell).

Meanwhile, 3GPP NR uses the concept of a cell to manage radio resources.A cell is defined as a combination of DL resources and UL resources,that is, a combination of DL CC and UL CC. A cell may be configured withDL resources alone, or a combination of DL resources and UL resources.When the carrier aggregation is supported, the linkage between thecarrier frequency of the DL resource (or DL CC) and the carrierfrequency of the UL resource (or UL CC) may be indicated by systeminformation. The carrier frequency refers to the center frequency ofeach cell or CC. A cell corresponding to the PCC is referred to as aPCell, and a cell corresponding to the SCC is referred to as an SCell.The carrier corresponding to the PCell in the DL is the DL PCC, and thecarrier corresponding to the PCell in the UL is the UL PCC. Similarly,the carrier corresponding to the SCell in the DL is the DL SCC and thecarrier corresponding to the SCell in the UL is the UL SCC. According toUE capability, the serving cell(s) may be configured with one PCell andzero or more SCells. In the case of UEs that are in the RRC_CONNECTEDstate but not configured for carrier aggregation or that do not supportcarrier aggregation, there is only one serving cell configured only withPCell.

As mentioned above, the term “cell” used in carrier aggregation isdistinguished from the term “cell” which refers to a certaingeographical area in which a communication service is provided by onebase station or one antenna group. That is, one component carrier mayalso be referred to as a scheduling cell, a scheduled cell, a primarycell (PCell), a secondary cell (SCell), or a primary SCell (PScell).However, in order to distinguish between a cell referring to a certaingeographical area and a cell of carrier aggregation, in the presentdisclosure, a cell of a carrier aggregation is referred to as a CC, anda cell of a geographical area is referred to as a cell.

FIG. 10 is a diagram showing an example in which a cross carrierscheduling technique is applied. When cross carrier scheduling is set,the control channel transmitted through the first CC may schedule a datachannel transmitted through the first CC or the second CC using acarrier indicator field (CIF). The CIF is included in the DCI. In otherwords, a scheduling cell is set, and the DL grant/UL grant transmittedin the PDCCH area of the scheduling cell schedules the PDSCH/PUSCH ofthe scheduled cell. That is, a search area for the plurality ofcomponent carriers exists in the PDCCH area of the scheduling cell. APCell may be basically a scheduling cell, and a specific SCell may bedesignated as a scheduling cell by an upper layer.

In the embodiment of FIG. 10 , it is assumed that three DL CCs aremerged. Here, it is assumed that DL component carrier #0 is DL PCC (orPCell), and DL component carrier #1 and DL component carrier #2 are DLSCCs (or SCell). In addition, it is assumed that the DL PCC is set tothe PDCCH monitoring CC. When cross-carrier scheduling is not configuredby UE-specific (or UE-group-specific or cell-specific) higher layersignaling, a CIF is disabled, and each DL CC can transmit only a PDCCHfor scheduling its PDSCH without the CIF according to an NR PDCCH rule(non-cross-carrier scheduling, self-carrier scheduling). Meanwhile, ifcross-carrier scheduling is configured by UE-specific (orUE-group-specific or cell-specific) higher layer signaling, a CIF isenabled, and a specific CC (e.g., DL PCC) may transmit not only thePDCCH for scheduling the PDSCH of the DL CC A using the CIF but also thePDCCH for scheduling the PDSCH of another CC (cross-carrier scheduling).On the other hand, a PDCCH is not transmitted in another DL CC.Accordingly, the UE monitors the PDCCH not including the CIF to receivea self-carrier scheduled PDSCH depending on whether the cross-carrierscheduling is configured for the UE, or monitors the PDCCH including theCIF to receive the cross-carrier scheduled PDSCH.

On the other hand, FIGS. 9 and 10 illustrate the subframe structure ofthe 3GPP LTE-A system, and the same or similar configuration may beapplied to the 3GPP NR system. However, in the 3GPP NR system, thesubframes of FIGS. 9 and 10 may be replaced with slots.

In addition, an NR system employs code block group (CBG)-basedtransmission unlike 3GPP LTE(-A). The following description is relatedthereto.

In 3GPP LTE(-A), a TB-cyclic redundancy code (TB-CRC) for detectingerror of a transport block (TB), which is a unit of data transmitted ina PDSCH, is attached to a TB, and the TB is divided into several codeblocks (CBs) for the efficiency of channel encoding. A CB-cyclicredundancy code (CB-CRC) for detecting error of a CB is attached to eachof the CBs. In a case where a PDSCH is received, a terminal transmits anACK if an error is not detected in a TB-CRC, and transmits an NACK if anerror is detected in a TB-CRC. That is, one HARQ-ACK per TB istransmitted. When an NACK is received, a base station determines that anerror has occurred in the prior TB, and performs HARQ retransmission ofall the CBs in the TB. Therefore, in an LTE system, if only one CB iswrongly received, all the CBs included in a TB are retransmitted.Therefore, there is a high possibility that inefficient retransmissionmay occur. In order to solve the problem, an NR system employs a schemeof: binding CBs configuring a TB, to form code block groups (CBGs) so asto allow HARQ-ACK transmission to be possible in units of CBGs; in acase of downlink transmission, notifying a base station of whether eachof the CBGs is successfully received, as a CBG level HARQ-ACK feedback;and performing, by the base station, HARQ retransmission of only CBGsthat failed to be received. Also in case of uplink transmission, the NRsystem may configure a scheme of: in addition to configuring HARQ-ACKtransmission in units of TBs for the uplink transmission, binding CBsconfiguring a TB for uplink transmission, to form code block groups(CBGs) so as to allow HARQ-ACK transmission to be possible in units ofCBGs; notifying a terminal of whether each of the CBGs is successfullyreceived, as a CBG level HARQ-ACK feedback; and performing, by theterminal, HARQ retransmission of only CBGs that failed to be received.

FIG. 11 illustrates an example of a scenario of placing a terminal and abase station in an LAA service environment. A frequency band targeted bya license-assisted access (LAA) service environment does not have a longwireless communication arrival distance due to the high-frequencycharacteristics. Considering this, the placement scenario for a terminaland a base station in an environment in which a conventional LTE-Lservice and an LAA service coexist may be an overlay model or aco-located model.

In the overlay model, a macro base station may perform wirelesscommunication with terminal X and terminal X′ in a macro region 32 byusing a licensed band carrier, and may be connected to multiple ratioremote heads (RRHs) through an X2 interface. Each of the RRHs mayperform wireless communication with terminal X or terminal X′ in apredetermined region 31 by using an unlicensed band carrier. The macrobase station and the RRHs have different frequency bands, and thus thereis no interference therebetween, however, the macro base station and theRRHs are required to perform fast data exchange therebetween through theX2 interface so as to use an LAA service through carrier aggregation asan auxiliary downlink channel of an LTE-L service.

In the co-located model, a pico/femto base station may perform wirelesscommunication with terminal Y by simultaneously using a licensed bandcarrier and an unlicensed band carrier. However, the pico/femto basestation may use an LTE-L service and an LAA service together only whendownlink transmission is performed. The coverage 33 of the LTE-L serviceand the coverage 34 of the LAA service may be different according to afrequency band, transmission power, and the like.

When LTE communication is performed in an unlicensed band, existingapparatuses (e.g. wireless LAN (Wi-Fi) apparatus) that communicate inthe unlicensed band are unable to demodulate an LAA message or data.Therefore, the existing apparatuses may determine an LAA message or datato be a kind of energy, and then perform an interference avoidanceoperation by an energy detection technique. That is, if an energycorresponding to an LAA message or data is smaller than −62 dBm or aparticular energy detection (ED) threshold, wireless LAN apparatuses maycommunicate while neglecting the message or data. Accordingly, aterminal that performs LTE communication in an unlicensed band may befrequently disturbed by the wireless LAN apparatuses.

Therefore, in order to effectively implement an LAA technology/service,it is required to allocate or reserve a particular frequency band duringa particular time interval. However, peripheral apparatuses thatcommunicate through an unlicensed band make an attempt to access on thebasis of an energy detection technique, and thus it is difficult toefficiently provide an LAA service. Therefore, in order to install anLAA technology, a study on a method for coexisting with an existingunlicensed band apparatus, and a method for efficiently sharing awireless channel is required to precede. That is, a strong coexistencemechanism by which an LAA apparatus does not affect an existingunlicensed band apparatus is required to be developed.

FIG. 12 illustrates an example of a conventional communication scheme(e.g. wireless LAN) operated in an unlicensed band. An apparatus thatoperates in an unlicensed band is operated on the basis of listen-beforetalk (LBT) most of the time, and thus performs a clear channelassessment (CCA) of sensing a channel before transmitting data.

Referring to FIG. 12 , before transmitting data, a wireless LANapparatus (e.g. an AP or an STA) performs carrier sensing to checkwhether a channel is being used (is busy). When a wireless signal havinga predetermined strength or higher is sensed in a channel in which thedata is to be transmitted, the wireless LAN apparatus determines thatthe channel is busy, and delays an access to the channel. This processis called a clear channel assessment, and a signal level for determiningwhether a signal is sensed is called a CCA threshold. Meanwhile, when awireless signal is not sensed in the channel, or a wireless signalhaving a strength smaller than the CCA threshold is sensed, theapparatus determines that the channel is in an idle state.

When the channel is determined to be in an idle state, a terminal havingdata to transmit performs a backoff procedure after a defer period (e.g.an arbitration interframe space (AIFS), a PCF IFS (PCIFS), etc.). Thedefer period implies a minimum time interval during which a terminal isrequired to wait after the channel has entered the idle state. Thebackoff procedure allows the terminal to wait more during apredetermined time interval after the defer period. For example, whilethe channel is in the idle state, the terminal may wait while reducing aslot time interval by a random number assigned to the terminal in acontention window (CW), and after all the slot time is exhausted, theterminal may attempt to access the channel.

When the channel is successfully accessed, the terminal may transmitdata through the channel. When data transmission is successful, the CWsize (CWS) is reset to an initial value (CWmin). Meanwhile, when datatransmission fails, the CWS is doubled. Accordingly, the terminalreceives a new random number assigned within the range of two times ofthe previous random number range, and then performs a backoff procedurein the next CW. In a wireless LAN, only an ACK is defined as receptionresponse information for data transmission. Therefore, when an ACK isreceived for data transmission, the CWS is reset to the initial value,and when feedback information for data transmission is not received, theCWS is doubled.

As described above, conventional communication in an unlicensed band isoperated on the basis of LBT most of the time, and thus LTE alsoconsiders LBT in LAA for coexistence with an existing apparatus.Specifically, a method for access to a channel in an unlicensed band inLTE may be divided into the following four categories according to thepresence or absence of LBT, or LBT application scheme.

Category 1: no LBT

-   -   a Tx entity does not perform an LBT procedure for transmission.

Category 2: LBT lacking random backoff

-   -   a TX entity senses whether the channel is in an idle state        during a first interval, without random backoff, to perform        transmission. That is, the Tx entity may perform transmission        through a channel immediately after the channel is sensed to be        in an idle state during the first interval. The first interval        is an interval having a pre-configured length immediately before        the Tx entity performs transmission. According to an embodiment,        the first interval may have a 25 μs length, but the present        disclosure is not limited thereto.

Category 3: LBT performing random backoff by using fixed size of CW

-   -   a Tx entity obtains a random number of N in a CW having a fixed        size and configures N as a backoff counter (or a backoff timer),        and performs backoff by using a configured backoff counter of N.        That is, in a backoff procedure, the Tx entity reduces the        backoff counter by one every time a channel is sensed to be in        an idle state during a pre-configured slot interval. The        pre-configured slot interval may be 9 μs, but the present        disclosure is not limited thereto. The backoff counter is        reduced from the initial value of N, and the value of the        backoff counter reaches 0, the Tx entity may perform        transmission. Meanwhile, in order to perform backoff, the Tx        entity senses whether the channel is in an idle state during a        second interval, first. The second interval may be configured on        the basis of a channel access priority class of the Tx entity,        and includes a 16 μs time interval and m number of consecutive        slot intervals. m is a value configured according to the channel        access priority class. When the channel is determined to be in        an idle state during the second interval, the Tx entity performs        channel sensing to reduce the backoff counter. Meanwhile, when        the channel is sensed to be in an occupied state in the backoff        procedure, the backoff procedure is stopped. After the backoff        procedure is stopped, when the channel is sensed to be in an        idle state during the second interval, the Tx entity may restart        backoff. As described above, if the channel is idle during the        slot interval of the backoff counter of N in addition to the        second interval, the Tx entity may perform transmission. The        backoff counter of N is obtained in the fixed size of CW.

Category 4: LBT performing random backoff by using changeable size of CW

-   -   a Tx entity obtains a random number of N in a CW having a        changeable size and configures N as a backoff counter (or a        backoff timer), and performs backoff by using a configured        backoff counter of N. More specifically, the Tx entity may        adjust the size of a CW on the basis of HARQ-ACK information for        previous transmission, and obtains the backoff counter of N in        the CW having the adjusted size. A detailed process for        performing backoff by the Tx entity is the same as that        described in category 3. When a channel is idle during the slot        interval of the backoff counter N in addition to the second        interval, the Tx entity may perform transmission. The backoff        counter of N is obtained in the changeable size of CW.

The Tx entity described in categories 1 to 4 may be a base station or aterminal. According to an embodiment of the present disclosure, a firsttype of channel access may indicate a channel access of category 4, anda second type of channel access may indicate a channel access ofcategory 2.

FIGS. 13 and 14 illustrate an example of a DL transmission process basedon category 4 LBT. Category 4 LBT may be used to ensure a fair channelaccess in comparison with Wi-Fi. Referring to FIGS. 13 and 14 , an LBTprocess includes an initial CCA (ICCA) and an extended CCA (ECCA). Inthe ICCA, a random backoff is not performed, and in the ECCA, a randombackoff is performed using a CW having a changeable size. The ICCA isapplied to a case where a channel is in an idle state at a time point atwhich signal transmission is required, and the ECCA is applied to a casewhere a channel is busy at a time point when signal transmission isrequired, or there is a DL transmission immediately before the timepoint. That is, whether a channel is in an idle state is determinedthrough the ICCA, and data transmission is performed after an ICCAperiod. If an interference signal is recognized, and thus it isimpossible to perform data transmission, a random backoff counter may beconfigured and then a data transmission time point may be obtainedthrough a defer period and the backoff counter.

Referring to FIG. 13 , a signal transmission process may be performed asfollows.

Initial CCA

-   -   S302: a base station identifies that a channel is in an idle        state.    -   S304: the base station checks whether signal transmission is        required. When signal transmission is not required, the base        station returns to operation S302, and when signal transmission        is required, operation S306 is proceeded.    -   S306: the base station checks whether the channel is in an idle        state during an ICCA defer period (BCCA). The ICCA defer period        is configurable. In an embodiment, the ICCA defer period may be        configured by a 16 μs interval and n number of consecutive CCA        slots. Here, n may be a positive integer, and one CCA slot        interval may be 9 μs. The number of CCA slots may be differently        configured according to a QoS class. The ICCA defer period may        be configured to be a proper value by considering a defer period        (e.g. DIFS or AIFS) of Wi-Fi. For example, the ICCA defer period        may be 34 μs. If the channel is in an idle state during the ICCA        defer period, the base station may perform a signal transmission        process (S308). If it is determined that the channel is busy in        the ICCA defer period, operation S312 is proceeded (ECCA).    -   S308: the base station may perform a signal transmission        process. If there is no signal transmission, operation S302 is        proceeded (ICCA), and if there is a signal transmission,        operation S310 is proceeded. Even in a case where a backoff        counter of N reaches 0 in operation S318, and thus operation        S308 is performed, if there is no signal transmission, operation        S302 is proceeded (ICCA), and if there is a signal transmission,        operation S310 is proceeded.    -   S310: when there is no required additional signal transmission,        operation S302 is proceeded (ICCA), and when an additional        signal transmission is required, operation S312 is proceeded        (ECCA).

Extended CCA

-   -   S312: the base station generates a random number N in a CW. N is        used as a counter in a backoff process, and is generated from        [0, q−1]. The CW is configured by q number of ECCA slots, and        the size of each of the ECCA slots may be 9 μs or 10 μs. The CW        size (CWS) is defined as q, and may be changeable in operation        S314. Thereafter, the base station proceeds with operation S316.    -   S314: the base station may update the CWS. The CWS q may be        updated to a value between X and Y. The X and Y values are        configurable parameters. The CWS update or adjustment may be        performed every time when N is generated (dynamic backoff), or        may be semi-statically performed at predetermined time intervals        (semi-static backoff). The CWS may be updated or adjusted on the        basis of exponential backoff or binary backoff. That is, the CWS        may be updated or adjusted to be a square of 2 or a multiple        of 2. In relation to PDSCH transmission, the CWS may be updated        or adjusted on the basis of a feedback/report (e.g. an        HARQ-ACK/NACK) of a terminal, or may be updated or adjusted on        the basis of sensing by the base station.    -   S316: the base station checks whether the channel is in an idle        state during an ECCA defer period (DeCCA). The ECCA defer period        is configurable. In an embodiment, the ECCA defer period may be        configured by a 16 μs interval and n number of consecutive CCA        slots. n may be a positive integer, and one CCA slot interval        may be 9 μs. The number of CCA slots may be differently        configured according to a QoS class. The ECCA defer period may        be configured to be a proper value by considering a defer period        (e.g. DIFS or AIFS) of Wi-Fi. For example, the ECCA defer period        may be 34 μs. If the channel is in an idle state during the ECCA        defer period, the base station proceeds with operation S318. If        it is determined that the channel is busy in the ECCA defer        period, the base station repeats operation S316.    -   S318: the base station checks whether N is 0. When N is 0, the        base station may perform a signal transmission process (S308).        In this case (i.e. N=0), the base station does not perform        transmission immediately, and performs a CCA check during at        least one slot to continue the ECCA process. When N is not equal        to 0 (i.e. N=0), operation S320 is proceeded.    -   S320: the base station senses a channel during one ECCA slot        interval (T). The ECCA slot size is 9 μs or 10 μs, and an actual        sensing time interval may be at least 4 μs.    -   S322: when it is determined that the channel is in an idle        state, operation S324 is proceeded. When it is determined that        the channel is busy, the base station returns to operation S316.        That is, one ECCA defer period is applied again after a channel        is in an idle state, and during the ECCA defer period, N is not        counted down.    -   S324: the base station reduces N by 1 (ECCA countdown).

The transmission process illustrated in FIG. 14 is substantiallyidentical or similar to that of FIG. 13 , and there is a differencetherebetween according to an implementation type. Therefore, fordetails, the description given with reference to FIG. 13 may be referredto.

Initial CCA

-   -   S402: a base station checks whether signal transmission is        required. When signal transmission is not required, operation        S402 is repeated, and when signal transmission is required,        operation S404 is proceeded.    -   S404: the base station identifies that a slot is in an idle        state. When the slot is in an idle state, operation S406 is        proceeded, and when the slot is busy, operation S412 is        proceeded (ECCA). The slot may correspond to a CCA slot        illustrated in FIG. 13 .    -   S406: the base station checks whether a channel is in an idle        state during a defer period (D). D may correspond to the ICCA        defer period illustrated in FIG. 13 . If the channel is in an        idle state during the defer period, the base station may perform        a signal transmission process (S408). If it is determined that        the channel is busy in the defer period, operation S404 is        proceeded.    -   S408: the base station may perform a signal transmission process        if the process is required.    -   S410: If there is no signal transmission, operation S402 is        proceeded (ICCA), and if there is a signal transmission,        operation S412 is proceeded (ECCA). Even in a case where a        backoff counter of N reaches 0 in operation S418, and thus        operation S408 is performed, if there is no signal transmission,        operation S402 is proceeded (ICCA), and if there is a signal        transmission, operation S412 is proceeded (ECCA).

Extended CCA

-   -   S412: the base station generates a random number N in a CW. N is        used as a counter in a backoff process, and is generated from        [0, q−1]. The CW size (CWS) is defined as q, and may be        changeable in operation S414. Thereafter, the base station        proceeds with operation S416.    -   S414: the base station may update the CWS. The CWS q may be        updated to a value between X and Y. The X and Y values are        configurable parameters. The CWS update or adjustment may be        performed every time when N is generated (dynamic backoff), or        may be semi-statically performed at predetermined time intervals        (semi-static backoff). The CWS may be updated or adjusted on the        basis of exponential backoff or binary backoff. That is, the CWS        may be updated or adjusted to be a square of 2 or a multiple        of 2. In relation to PDSCH transmission, the CWS may be updated        or adjusted on the basis of a feedback/report (e.g. an        HARQ-ACK/NACK) of a terminal, or may be updated or adjusted on        the basis of base station sensing.    -   S416: the base station checks whether the channel is in an idle        state during the defer period (D). D may correspond to the ECCA        defer period illustrated in FIG. 13 . In operations S406 and        S416, the values of D may be the same. If the channel is in an        idle state during the defer period, the base station proceeds        with operation S418. If it is determined that the channel is        busy in the defer period, the base station repeats operation        S416.    -   S418: the base station checks whether N is 0. when N is 0, the        base station may perform a signal transmission process (S408).        In this case (N=0), the base station does not perform        transmission immediately, and performs a CCA check during at        least one slot to continue the ECCA process. When N is not equal        to 0 (i.e. N>0), operation S420 is proceeded.    -   S420: the base station may select one of an operation of        reducing N by 1 (ECCA countdown) or an operation of not reducing        N (self-deferral). A self-deferral operation may be performed        according to an implementation or selection by the base station.        At the time of a self-deferral, the base station performs        neither sensing for energy detection nor ECCA countdown.    -   S422: the base station may select one of an operation of not        performing sensing for energy detection or an energy detection        operation. If the base station does not perform sensing for        energy detection, operation S424 is proceeded. In a case where        the energy detection operation is performed, when an energy        level is equal to or lower than an energy detection threshold        (i.e. idle), operation S424 is proceeded. When the energy level        exceeds the energy detection threshold (i.e. busy), the base        station returns to operation S416. That is, one defer period is        applied again after a channel is in an idle state, and during        the defer period, N is not counted down.    -   S424: operation S418 is proceeded.

FIG. 15 illustrates an example in which a base station performs a DLtransmission in an unlicensed band. A base station may aggregate one ormore licensed band cells (for convenience, may be referred to as anLTE-L cell or an NR-licensed cell), and one or more unlicensed bandcells (for convenience, an LTE-U cell, an NR-unlicensed cell, or an NR-Ucell). In FIG. 15 , it is assumed that one LTE-L cell and one LTE-U cellare aggregated for communication with a terminal. The LTE-L cell may bea PCell, and the LTE-U cell may be an SCell. In the LTE-L cell, the basestation may exclusively use frequency resources, and perform aconventional operation according to LTE. Therefore, a radio frame may beconfigured by regular subframes (rSFs) each having a length of 1 ms (seeFIG. 2 ), and a DL transmission (e.g. a PDCCH or a PDSCH) may beperformed for each subframe (see FIG. 1 ). In the LTE-U cell, DLtransmission is performed on the basis of LBT for the coexistence withan existing apparatus (e.g. a Wi-Fi apparatus). Moreover, in order toeffectively implement an LTE-U technology/service, it is required toallocate or reserve a particular frequency band during a particular timeinterval. Therefore, in the LTE-U cell, DL transmission may be performedthrough a set of one or more consecutive subframes after LBT (DLtransmission burst). A DL transmission burst may start with a regularsubframe (rSF) as illustrated in FIG. 15(a), or may start with a partialsubframe (pSF) as illustrated in FIG. 15(b) according to an LBTsituation. A pSF is a part of a subframe, and may include the secondslot of the subframe. In addition, the DL transmission burst may endwith an rSF or a pSF.

Hereinafter, a method for adaptively adjusting a CWS in an unlicensedband at the time of a channel access is proposed. A CWS may be adjustedon the basis of a user equipment (UE) feedback, and a UE feedback usedfor CWS adjustment may include an HARQ-ACK response, and a CQI/PMI/RI.In the present disclosure, a method for adaptively adjusting a CWS onthe basis of an HARQ-ACK response is proposed. An HARQ-ACK responseincludes an ACK, an NACK, and a DTX.

As illustrated with reference to FIG. 12 , a CWS is adjusted on thebasis of an ACK also in Wi-Fi. If an ACK feedback is received, a CWS isreset to a minimum value (CWmin), and if an ACK feedback is notreceived, the CWS is increased. However, in a cellular system (e.g.LTE), a CWS adjusting method considering multiple accesses is required.

First, terms are defined as follows for description of the presentdisclosure.

-   -   a set of HARQ-ACK feedback values (an HARQ-ACK feedback set):        meaning an HARQ-ACK feedback value(s) used for CWS        update/adjustment. The HARQ-ACK feedback set correspond to        HARQ-ACK feedback values which have already been decoded and are        available at a time point at which a CWS is determined. The        HARQ-ACK feedback set includes an HARQ-ACK feedback value(s) for        one or more DL (channel) transmissions (e.g. a PDSCH) on an        unlicensed band (e.g. an LTE-U cell). The HARQ-ACK feedback set        may include an HARQ-ACK feedback value(s) for a DL (channel)        transmission (e.g. a PDSDH), for example, multiple HARQ-ACK        feedback values fed back from multiple terminals. An HARQ-ACK        feedback value indicates reception response information for a        transport block or a PDSCH, and may indicate an ACK, a NACK, a        DTX, and an NACK/DTX. According to context, the HARQ-ACK        feedback value may be used together with an HARQ-ACK        value/bit/response/information.    -   reference window: meaning a time interval in which a DL        transmission (e.g. a PDSCH) corresponding to an HARQ-ACK        feedback set is performed in an unlicensed band (e.g. an LTE-U        cell). The reference window may be defined in units of SFs. The        reference window will be described and proposed in more detail        later.

In LTE, an HARQ-ACK feedback value may indicate only an ACK or an NACK,or further indicate a DTX according to an HARQ-ACK feedback scheme, aPUCCH format, or the like. For example, if PUCCH format 3 is configuredby an HARQ-ACK feedback method, an HARQ-ACK value may only indicate anACK and an NACK. Meanwhile, a channel selection scheme using PUCCHformat 1b is configured by an HARQ-ACK feedback method, an HARQ-ACKvalue may indicates an ACK, an NACK, a DTX, and an NACK/DTX.

Referring to FIG. 16 , after a base station transmits a n-th DLtransmission burst in an unlicensed band (e.g. an LTE-U cell) (S502), ifan additional DL transmission is needed, the base station may transmitan (n+1)th DL transmission burst on the basis of an ECCA (S512).Specifically, when a channel in an unlicensed band is empty during anECCA defer period, the base station additionally performs backoff in aCW (S510). The base station may generate a random number N in a CW (e.g.[0, q−1]) (S508), and perform backoff as many slots as the random numberN (S510). In the present disclosure, the CWS may be adjusted on thebasis of HARQ-ACK feedback values from terminals (S506). The HARQ-ACKfeedback values used for CWS adjustment includes HARQ-ACK feedbackvalues related to the latest DL transmission burst (the n-th DLtransmission burst). The HARQ-ACK feedback values used for CWSadjustment include HARQ-ACK feedback values related to a DL transmissionon a reference window in the DL transmission burst (S504).

In the above description of the present disclosure so far, an LAA cellbased on LTE is defined as an LTE-U cell, however, also identically forNR, an NR licensed cell may be replaced with an LTE-L cell, and an NRunlicensed cell may also be replaced with an LTE-U cell, for applicationto the present disclosure. However, with respect to a point which may bedifferent with using an NR unlicensed cell, if there is a referencerelated thereto in a detailed matter of the present disclosure, thereference is applied to the NR-unlicensed cell.

<BWP Operation for Wideband Operation in NR System>

FIG. 17 illustrates an example of a method for configuring, forterminals, a BWP having a bandwidth equal to or smaller than thebandwidth of a carrier (or a cell) in a 3GPP NR system.

Referring to FIG. 17 , in a 3GPP NR system, terminals may performtransmission or reception using a bandwidth equal to or smaller than thebandwidth of a carrier (or a cell). To this end, a terminal may receivea configuration of multiple BWPs from a base station. Each of the BWPsis configured by consecutive PRBs. Referring to FIG. 17 -(a), the BWPsmay be separated to be not overlapped with each other. One or multipleBWPs among the BWPs separated to be not overlapped may be allocated andconfigured for terminals. The terminals may perform transmission orreception with the base station by using the allocated and configuredBWPs. Referring to FIG. 17 -(b), BWPs may be separated while beingoverlapped in a carrier bandwidth. One BWP may be configured to beincluded in another BWP. One or multiple BWPs among the BWPs separatedwhile being overlapped may be allocated and configured for terminals.The terminals may perform transmission or reception with the basestation by using one BWP among the allocated and configured BWPs.

FIG. 18 illustrates an example of a method for configuring or allocatinga CORESET in a BWP assigned to a terminal.

Referring to FIG. 18 , when multiple BWPs are assigned to a terminal, atleast one CORESET may be configured or assigned for each of the BWPs.Referring to FIGS. 18 -(a) and 18-(b), in both a case when BWPs areconfigured to be not overlapped with each other, and a case when BWPsare configured to be overlapped, a CORESET for each of the BWPs may bepositioned in the time/frequency resource region occupied by each BWP.In other words, CORESET #1 for bandwidth part #1 may exist within thePRBs of the time/frequency resource region occupied by bandwidth part#1, and CORESET #2 for bandwidth part #2 may exist within the PRBs ofthe time/frequency resource region occupied by bandwidth part #2.Referring to FIG. 18 -(b), when bandwidth parts are configured to beoverlapped with each other, PRBs occupied by a CORESET may be positionedin another bandwidth part even though the PRBs are still in thetime/frequency resource region of the bandwidth part of the CORESET. Inother words, CORESET #2 for bandwidth part #2 may overlap with the PRBsof the time/frequency resource region occupied by bandwidth part #1.

In a time division duplex (TDD) cell, a maximum of four downlink BWPs(DL BWPs) and a maximum of four uplink BWPs (UL BWPs) per cell may beconfigured. For a terminal, one DL BWP and one UL BWP may besimultaneously activated in one cell. In a frequency division duplex(FDD) cell, a maximum of four DL/UL BWP pairs per cell may beconfigured. For a terminal, one DL/UL BWP may be simultaneouslyactivated in one cell. A terminal does not expect to receive any signalin a PRB other than an activated DL BWP, and does not expect to transmitany signal in a PRB other than an activated UL BWP. A terminal movesfrom one BWP to another BWP, that is, the base station instructs theterminal to deactivate a currently used BWP and activate a new BWP byusing downlink control information (DCI). More specifically, DCIscheduling a PDSCH includes a bandwidth part indicator (BPI) indicatinga BWP to be activated, so as to change a DL BWP of a terminal in a TDDcell. That is, if DCI scheduling a PDSCH is received, a terminal mayidentify a BWP through which the PDSCH is to be transmitted, through aBPI. Furthermore, the terminal may identify PRBs of the BWP, throughwhich the PDSCH is to be transmitted, through resource allocation (RA)information of the DCI. Similarly, DCI scheduling a PUSCH includes abandwidth part indicator (BPI) indicating a BWP to be activated, so asto change a UL BWP of a terminal in a TDD cell. That is, if DCIscheduling a PUSCH is received, a terminal may identify a BWP throughwhich the PUSCH is to be transmitted, through a BPI. Furthermore, theterminal may identify PRBs of the indicated BWP, through which the PUSCHis to be transmitted, through RA information of the DCI. In an FDD cell,a BWP value of DCI scheduling a PDSCH and a PUSCH may indicate one ofDL/UL BWP pairs.

A wireless communication apparatus operated in a wireless communicationsystem according to an embodiment of the present disclosure may performan LBT procedure in a unit of predesignated bandwidths in order toperform the LBT procedure in an unlicensed band. The predesignatedbandwidth may be called an LBT bandwidth, an LBT subband, or an LBTbasic bandwidth. For convenience of explanation, in the followingdescription, the predesignated bandwidth is called a basic bandwidth.Specifically, when accessing a channel, a wireless communicationapparatus may determine whether the channel is idle in a unit of basicbandwidths. In a detailed embodiment, a wireless communication apparatusmay determine whether a channel is idle in a unit of predesignated basicbandwidths, and determine whether to perform transmission in thechannel, on the basis of the determination on whether the channel isidle. In addition, the basic bandwidth may be 20 MHz. The 20 MHz sizemay be determined in consideration of the coexistence with anotherwireless communication apparatus (e.g., a wireless LAN apparatus) usingan unlicensed band. In the present specification, a wirelesscommunication apparatus may be called a terminal or a base station. Inaddition, the wireless communication apparatus may be called both aterminal and a base station. Therefore, both channel access for ULtransmission and channel access for DL transmission may be performed ina unit of basic bandwidths. As described above, when a wirelesscommunication apparatus performs channel access in a unit of basicbandwidths in an unlicensed band, a method for performing channel accessby using a bandwidth larger than the basic bandwidth, or performingchannel access in a BWP having a bandwidth larger than the basicbandwidth may be a problem. The BWP corresponds to consecutive PRB setsselected from among consecutive multiple RB subsets for given carriersand given numerology, as described above. A base station may configureone or more DL BWPs for the downlink for a terminal, and may performtransmission to the terminal through one downlink active DL BWP amongthe one or more configured DL BWPs. Furthermore, the base station mayconfigure one or more UL BWPs for the uplink for the terminal, and mayschedule a resource for uplink transmission of the terminal through oneuplink active UL BWP among the one or more configured UL BWPs.Specifically, in a case where a frequency resource corresponding to onebasic bandwidth is idle, but another resource corresponding to the basicbandwidth is being used (busy), a method for accessing a channel by awireless communication apparatus may be a problem. This is because, in aBWP, in a case where a frequency resource corresponding to one basicbandwidth is idle, but another resource corresponding to the basicbandwidth is busy, if a wireless communication apparatus fails totransmit data in the BWP, frequency efficiency (spectral efficiency) maybe reduced.

In a detailed embodiment, a base station may assign the bandwidth of aBWP to be the basic bandwidth. In this case, the base station mayperform downlink transmission in multiple BWPs at the same time. Aterminal may perform uplink transmission in multiple BWPs at the sametime. In these embodiments, the specific operation of the base stationand the terminal may be the same as a channel access operation inmulti-carriers, defined in 3GPP TS 36.213 v14.8.0. In another detailedembodiment, a base station may configure the bandwidth of a BWP to be aninteger multiple of the basic bandwidth. A detailed method foraccessing, by a wireless communication apparatus, a channel by using aBWP in a wireless communication system operated in an unlicensed bandwill be described.

A base station may configure multiple BWPs for a terminal in anunlicensed band. Specifically, the base station may configure multipledownlink BWPs for the terminal in an unlicensed band. The base stationmay activate multiple BWPs for the terminal in the unlicensed band. Inthis embodiment, an operation method of the base station and theterminal will be described first. The base station may indicateinformation on an activated BWP to the terminal by transmittingbandwidth part (BWP)-related signaling. The terminal may receive theBWP-related signaling from the base station, and may determine a BWPactivated for the terminal. Specifically, the base station may configureone or more activated downlink BWPs for the terminal among multipledownlink BWPs through dedicated RRC signaling. Alternatively, asdescribed above, the base station may indicate an activated BWP amongBWPs configured for the terminal, through DCI. The terminal may receiveDCI, and determine an activated BWP on the basis of the DCI.

When a channel is successfully accessed by the base station in one ormore BWPs, the base station may transmit a PDSCH in the one or more BWPsin which the channel access has been successful. That is, if there aremultiple BWPs in which a channel is successfully accessed by the basestation, the base station may transmit a PDSCH in the multiple BWPs. Thebase station may transmit PDCCHs scheduling PDSCHs in BWPs in which thePDSCHs are to be transmitted, and each of the PDCCHs may includescheduling information of a PDSCH transmitted in a BWP in which acorresponding PDCCH is transmitted. The scheduling information of aPDSCH indicates information on time and frequency resources for thetransmission of the PDSCH. When multiple BWPs are activated among BWPsconfigured for the terminal, the terminal may not determine, among themultiple activated BWPs, a BWP in which a channel will be successfullyaccessed by the base station. Therefore, the terminal may monitor aPDCCH in a CORESET configured in each of the multiple activated BWPs, soas to attempt to receive the PDCCH. The terminal may receive a PDSCH ineach BWP by using PDSCH scheduling information included in a receivedPDCCH. The terminal may monitor a PDCCH in all BWPs configured for theterminal. Specifically, the terminal may monitor a PDCCH in a CORESET ofall BWPs configured for the terminal. In addition, the terminal mayreceive a PDSCH in a corresponding BWP on the basis of PDSCH schedulinginformation included in a received PDCCH. In this embodiment, theterminal is required to monitor a PDCCH in all BWPs configured for theterminal, and thus complexity for blind decoding of the PDCCH may beincreased. Furthermore, the power consumed by the terminal to receivethe PDCCH may be also increased. In the present specification, thesuccess of channel access may indicate a case where transmission isallowed in a corresponding channel according to a channel accessprocedure. The channel access procedure may indicate an LBT proceduredescribed above.

The base station may configure different BWPs to have differentfrequency resources. In addition, the base station may configuredifferent BWPs to have an overlapped frequency resource. For example, ifit is configured that different BWPs are overlapped with each other, apart of a first BWP frequency resource and a part of a second BWPfrequency resource may be same. Moreover, the second BWP frequencyresource may be included in the first BWP frequency resource. Forconvenience of explanation, if the frequency resources of different BWPsare overlapped with each other, the BWPs are called overlapped BWPs. Thebase station configures a CORESET for each of BWPs, and the terminalmonitors a PDCCH in a CORESET resource of each of the BWPs. If there areoverlapped BWPs, the terminal may sequentially monitor a PDCCH in theoverlapped BWPs according to the priorities of the BWPs. In thisembodiment, when the terminal receives a PDCCH in one BWP, the terminalmay not monitor a PDCCH in a BWP having a priority lower than that ofthe BWP in which the PDCCH is received. The priority may be configuredon the basis of the bandwidth size of the BWP. In a detailed embodiment,a BWP having a wider bandwidth may have a higher priority. When thebandwidth of a first BWP is larger than that of a second BWP, theterminal may monitor a PDCCH in the first BWP and then monitor a PDCCHin the second BWP. In another detailed embodiment, a BWP having anarrower bandwidth may have a higher priority. When the bandwidth of afirst BWP is smaller than that of a second BWP, the terminal may monitora PDCCH in the first BWP and then monitor a PDCCH in the second BWP.This operation may be efficient in a case where a base station mayperform transmission in a BWP only when a channel is successfullyaccessed in all basic bandwidths included in the BWP. This is because,in a case where a base station may perform transmission in a BWP onlywhen a channel is successfully accessed in all basic bandwidths includedin the BWP, it is highly probable that the terminal transmits a PDCCH ina BWP having a narrow bandwidth.

In another embodiment, even when a channel is successfully accessed bythe base station in multiple BWPs, the base station may transmit a PDSCHin one BWP among the multiple BWPs in which the channel is successfullyaccessed. The base station may determine a BWP in which a PDSCH is to betransmitted, among the multiple BWPs in which the channel issuccessfully accessed, according to the priorities. The base station maytransmit a PDCCH scheduling a PDSCH in a BWP in which the PDSCH is to betransmitted. The terminal may determine the sequence of multiple BWPs inwhich a PDCCH is to be monitored, on the basis of the priorities of theBWPs. If multiple BWPs are activated for the terminal, the terminal maysequentially monitor a PDCCH in the multiple BWPs according to thepriorities of the multiple BWPs. When the terminal receives a PDCCH inone BWP, PDCCH monitoring may be omitted in BWPs other than the BWP inwhich the PDCCH is received. Specifically, when the terminal receives aPDCCH scheduling a PDCSH in one BWP, monitoring of a PDCCH scheduling aPDSCH may be omitted in BWPs other than the BWP in which the PDCCH isreceived.

The priority may be determined on the basis of the index of the BWP. Ina detailed embodiment, a BWP having a greater index may have a higherpriority. For example, if the base station has successfully accessed achannel in a first BWP and a second BWP, and the index of the first BWPis greater than the index of the second BWP, the base station maydetermine the first BWP, as a BWP in which a PDSCH is to be transmitted,among the first BWP and the second BWP. The terminal may monitor a PDCCHin the first BWP and then monitor a PDCCH in the second BWP. In anotherdetailed embodiment, a BWP having a smaller index may have a higherpriority. For example, if the base station has successfully accessed achannel in a first BWP and a second BWP, and the index of the first BWPis smaller than the index of the second BWP, the base station maydetermine the first BWP, as a BWP in which a PDSCH is to be transmitted,among the first BWP and the second BWP. The terminal may monitor a PDCCHin the first BWP and then monitor a PDCCH in the second BWP. When theterminal receives a PDCCH in a BWP having a high priority related tomonitoring the PDCCH, the terminal may omit PDCCH monitoring in BWPsother than the BWP in which the PDCCH is received. Specifically, whenthe terminal receives a PDCCH scheduling a PDCSH in a BWP having a highpriority related to monitoring the PDCCH, monitoring of a PDCCHscheduling a PDSCH may be omitted in BWPs other than the BWP in whichthe PDCCH is received.

In another detailed embodiment, the priority may be determined on thebasis of the bandwidth of the BWP. Specifically, a BWP having a narrowerbandwidth may have a higher priority. For example, if the base stationhas successfully accessed a channel in a first BWP and a second BWP, andthe bandwidth of the first BWP is smaller than the bandwidth of thesecond BWP, the base station may determine the first BWP, as a BWP inwhich a PDSCH is to be transmitted, among the first BWP and the secondBWP. The terminal may monitor a PDCCH in the first BWP and then monitora PDCCH in the second BWP. In another detailed embodiment, a BWP havinga wider bandwidth may have a higher priority. For example, if the basestation has successfully accessed a channel in a first BWP and a secondBWP, and the bandwidth of the first BWP is larger than the bandwidth ofthe second BWP, the base station may determine the first BWP, as a BWPin which a PDSCH is to be transmitted, among the first BWP and thesecond BWP. The terminal may monitor a PDCCH in the first BWP and thenmonitor a PDCCH in the second BWP. In addition, in the aboveembodiments, if multiple BWPs have the same bandwidths, the prioritiesmay be determined on the basis of the indexes of the BWPs.

In another detailed embodiment, the base station may configure one ormore BWPs for the terminal in an unlicensed band, and may be limited toactivate only one BWP among the one or more configured BWPs.Accordingly, even if multiple BWPs are configured for the terminal in anunlicensed band, the base station may activate only one BWP for theterminal in the unlicensed band. In this embodiment, an operation methodof the base station and the terminal will be described first.

The base station may transmit a PDSCH to the terminal in a BWP only whena channel is successfully accessed in all basic bandwidths included inthe BWP. If a channel is successfully accessed by the base station inall basic bandwidths included in a BWP, the base station may transmit aPDCCH scheduling a PDSCH to the terminal in the BWP. The terminal maymonitor a PDCCH in an active BWP among BWPs configured for the terminal.Specifically, the terminal may monitor a PDCCH in a CORESET of an activeBWP among BWPs configured for the terminal. The terminal monitors aPDCCH in only one BWP, and thus it may be prevented that the complexityof the terminal is increased for the operation in an unlicensed band.Moreover, it may be prevented that the power consumption efficiency ofthe terminal is decreased in an unlicensed band. However, in a casewhere a base station performs transmission in a BWP only when a channelis successfully accessed in all basic bandwidths included in the BWP,the spectral efficiency of downlink transmission from the base stationto the terminal may be decreased.

In a case where a channel is successfully accessed by the base stationin even one of basic bandwidths included in a BWP, the base station maytransmit a PDSCH to the terminal in the BWP by using one or morebandwidths in which the channel access has been successful. In a casewhere a channel is successfully accessed by the base station in even oneof basic bandwidths included in a BWP, the base station may transmit aPDCCH scheduling a PDSCH to the terminal in the BWP by using one or morebandwidths in which the channel access has been successful. Through thisembodiment, the base station may increase a spectral efficiency for thetransmission of a PDCCH. However, the terminal is unable to identify abasic bandwidth, among one or more basic bandwidths included in a BWP,in which a channel has been successfully accessed by the base station.Therefore, the terminal may monitor a PDCCH in a CORESET configured in aBWP. However, in a case where a CORESET is configured in a unit of BWPs,and the base station fails to access a channel in one bandwidth amongbasic bandwidths included in a BWP, the base station is unable to use apartial bandwidth of the CORESET, and thus may fail to transmit a PDCCHin the CORESET. Accordingly, the terminal may fail to receive a PDCCH inthe CORESET. Therefore, the base station may configure a CORESET withina basic bandwidth in a BWP. Specifically, if the base station configuresa CORESET in a BWP, the base station may configure the CORESET within abasic band. The terminal may assume that the base station may transmit aPDCCH in a CORESET in a basic bandwidth, and then may monitor the PDCCH.In a case where the size of the bandwidth of a BWP configured for theterminal, that is, the number of basic bandwidths is increased, theterminal monitors a PDCCH in an increased number of CORESETs becauseeach CORESET is allowed to be configured within a basic bandwidth.Therefore, there are shortcomings in that the complexity and powerconsumption of the terminal may be increased by PDCCH blind decoding.Therefore, a method by which a terminal may efficiently monitor a PDCCHis required. Specifically, a method by which a terminal efficientlymonitors a PDCCH when a CORESET is configured in a basic bandwidth, thatis, a CORESET has a bandwidth equal to or smaller than that of the basicbandwidth, is required. The method will be explained with reference toFIGS. 19 to 21 .

FIG. 19 shows an operation of, when a base station according to anembodiment of the present disclosure configures a BWP including one ormore basic bandwidths, transmitting a PDCCH in a CORESET configured ineach of the basic bandwidths, on the basis of the priorities of thebasic bandwidths, and transmitting a PDSCH in the BWP.

In a case where a channel is successfully accessed by the base stationin multiple basic bandwidths each including a CORESET in a BWP, the basestation may transmit a PDCCH scheduling a PDSCH to the terminal in onebasic bandwidth among the multiple basic bandwidths in which the channelaccess has been successful. The base station may divide a BWP intomultiple basic bandwidths each including a CORESET, and may designate apriority of each of the multiple basic bandwidths. Each of the multiplebasic bandwidths may have a unique priority. In a case where a channelis successfully accessed by the base station in multiple basicbandwidths each including a CORESET in a BWP, the base station maydetermine, as a bandwidth in which a PDCCH is to be transmitted, a basicbandwidth having the highest priority among the basic bandwidths inwhich the base station has succeeded in the channel access. That is, ina case where a channel is successfully accessed by the base station inmultiple basic bandwidths each including a CORESET in a BWP, the basestation may transmit a PDCCH to the terminal in a basic bandwidth havingthe highest priority among the basic bandwidths in which the basestation has succeeded in the channel access. For convenience ofexplanation, a basic bandwidth having the highest priority among basicbandwidths in which the base station may transmit a PDCCH and hassuccessfully accessed a channel, is called a top-priority basicbandwidth. The terminal may monitor a PDCCH on the basis of thepriorities of basic bandwidths. Specifically, the terminal may determinethe sequence of basic bandwidths in which a PDCCH is to be monitored, onthe basis of the priorities of the basic bandwidths. In a case whereCORESETs are configured in basic bandwidths, the terminal maysequentially monitor a PDCCH in CORESETs of multiple basic bandwidthsaccording to the priorities of the multiple basic bandwidths. Forexample, when the terminal has failed to receive a PDCCH in a CORESETconfigured in a bandwidth having the highest priority among basicbandwidths, the terminal monitors a PDCCH in a CORESET configured in abasic bandwidth having the second highest priority. When the terminalreceives a PDCCH in one basic bandwidth, monitoring a PDCCH in theremaining basic bandwidths may be omitted. Specifically, when theterminal receives a PDCCH scheduling a PDCSH in one basic bandwidth,monitoring of a PDCCH scheduling a PDSCH may be omitted in basicbandwidths other than the basic bandwidth in which the PDCCH isreceived.

In addition, a PDCCH may schedule a PDCSH transmitted in a basicbandwidth in which the base station has succeeded in channel access. APDCCH may schedule a PDCSH transmitted in basic bandwidths other than atop-priority basic bandwidth, as well as a PDSCH transmitted in thetop-priority basic bandwidth. The base station may determine one or morebasic bandwidths in which a PDSCH is to be transmitted, on the basis ofa top-priority basic bandwidth. The terminal may receive a PDSCH on thebasis of PDSCH scheduling information included in a received PDCCH.

In addition, the base station may determine a basic bandwidth in which aPDSCH is to be transmitted, by combining a result of channel access inthe top-priority basic bandwidth, and a result of channel access inother basic bandwidths in a corresponding BWP. In a detailed embodiment,when the base station has also successfully accessed a channel in abasic bandwidth adjacent to the top-priority basic bandwidth, the basestation may transmit a PDSCH on the basis of the top-priority basicbandwidth and the basic bandwidth, in which the base station hassucceeded in channel access and which is adjacent to the top-prioritybasic bandwidth. The base station may transmit a PDSCH through abandwidth having the size of an integer multiple of the basic bandwidth(e.g., 20 MHz*M, wherein M={1, 2, 3, 4, . . . , N}, and N is a naturalnumber). In another detailed embodiment, the base station may transmit aPDSCH through a bandwidth having a size obtained by multiplying thebasic bandwidth by a power of 2 (e.g., 20 MHz*2{circumflex over ( )}L,wherein L={0, 1, 2, 3, . . . , X} and X is a natural number). Each ofthe LBT units shown in FIG. 19 indicates a basic bandwidth.

FIG. 19 -(a) shows a case where a base station transmits a PDSCH througha bandwidth having the size of an integer multiple of a basic bandwidth.Case 1 shows an instance where the base station has successfullyaccessed a channel in a basic bandwidth (primary LBT unit) having thehighest priority, and has failed to access a channel in a basicbandwidth (secondary LBT unit) having the second highest priority. Incase 1, the base station is allowed to transmit a PDSCH through onebasic bandwidth (1st LBT unit). Case 2 shows an instance where the basestation has successfully accessed a channel in a basic bandwidth(primary LBT unit) having the highest priority and a basic bandwidth(secondary LBT unit) having the second highest priority, and has failedto access a channel in a basic bandwidth (thirdly LBT unit) having thethird highest priority. In case 2, the base station is allowed totransmit a PDSCH through two basic bandwidths (1st LBT unit and 2nd LBTunit). Case 3 shows an instance where the base station has successfullyaccessed a channel in a basic bandwidth (primary LBT unit) having thehighest priority, a basic bandwidth (secondary LBT unit) having thesecond highest priority, and a basic bandwidth (thirdly LBT unit) havingthe third highest priority, and has failed to access a channel in abasic bandwidth (fourthly LBT unit) having the fourth highest priority.In case 3, the base station is allowed to transmit a PDSCH through threebasic bandwidths (1st LBT unit, 2nd LBT unit, and 3rd LBT unit). Case 4shows an instance where the base station has successfully accessed achannel in all (N number of) basic bandwidths. In case 4, the basestation is allowed to transmit a PDSCH through N number of basicbandwidths (1st LBT unit, 2nd LBT unit, 3rd LBT unit, . . . , and NthLBT unit). Case 5 shows an instance where the base station hassuccessfully accessed a channel in a basic bandwidth (secondary LBTunit) having the second highest priority, and has failed to access achannel in a basic bandwidth (primary LBT unit) having the highestpriority and a basic bandwidth (thirdly LBT unit) having the thirdhighest priority. In case 5, the base station is allowed to transmit aPDSCH through one basic bandwidth (2nd LBT unit). Case 6 shows aninstance where the base station has successfully accessed a channel in abasic bandwidth (secondary LBT unit) having the second highest priorityand a basic bandwidth (thirdly LBT unit) having the third highestpriority, and has failed to access a channel in a basic bandwidth(primary LBT unit) having the highest priority and a basic bandwidth(fourthly LBT unit) having the fourth highest priority. In case 6, thebase station is allowed to transmit a PDSCH through two basic bandwidths(2nd LBT unit and 3rd LBT unit). Case 7 shows an instance where the basestation has successfully accessed a channel in all basic bandwidthsexcept for a basic bandwidth (primary LBT unit) having the highestpriority. In this case, PDSCH transmission through (N−1) number of basicbandwidths (2nd LBT unit, 3rd LBT unit, . . . Nth LBT unit) is allowed.Case 8 shows an instance where the base station has successfullyaccessed a channel in a basic bandwidth (thirdly LBT unit) having thethird highest priority, and has failed to access a channel in a basicbandwidth (primary LBT unit) having the highest priority, a basicbandwidth (secondary LBT unit) having the second highest priority, and abasic bandwidth (fourthly LBT unit) having the fourth highest priority.In case 8, the base station is allowed to transmit a PDSCH through onebasic bandwidth (thirdly LBT unit). Case 9 shows an instance where thebase station has successfully accessed a channel in all basic bandwidthsexcept for a basic bandwidth (primary LBT unit) having the highestpriority and a basic bandwidth (secondary LBT unit) having the secondhighest priority. In case 9, the base station is allowed to transmit aPDSCH through (N−2) number of basic bandwidths (3rd LBT unit, . . . ,Nth LBT unit). Case 10 shows an instance where the base station hassuccessfully accessed a channel only in a basic bandwidth (Nth LBT unit)having the lowest priority. In case 10, the base station is allowed totransmit a PDSCH through one basic bandwidth (Nth LBT unit).

FIG. 19(b) shows a case where a base station transmits a PDSCH through abandwidth having a size obtained by multiplying a basic bandwidth by apower of 2. Case 1 shows an instance where the base station hassuccessfully accessed a channel in a basic bandwidth (a primary LBTunit) having the highest priority, and has failed to access a channel ina basic bandwidth (a secondary LBT unit) having the second highestpriority. In case 1, the base station is allowed to transmit a PDSCHthrough one basic bandwidth (1st LBT unit). Case 2 shows an instancewhere the base station has successfully accessed a channel in a basicbandwidth (primary LBT unit) having the highest priority and a basicbandwidth (secondary LBT unit) having the second highest priority, andhas failed to access a channel in at least one of a basic bandwidth(thirdly LBT unit) having the third highest priority and a basicbandwidth (fourthly LBT unit) having the fourth highest priority. Incase 2, the base station is allowed to transmit a PDSCH through twobasic bandwidths (1st LBT unit and 2nd LBT unit). Case 3 shows aninstance where the base station has successfully accessed a channel inall (N number of) basic bandwidths. In case 3, the base station isallowed to transmit a PDSCH through N number of basic bandwidths. Case 4shows an instance where the base station has successfully accessed achannel in a basic bandwidth (secondary LBT unit) having the secondhighest priority, and has failed to access a channel in a basicbandwidth (primary LBT unit) having the highest priority and a basicbandwidth (thirdly LBT unit) having the third highest priority. In case4, the base station is allowed to transmit a PDSCH through one basicbandwidth (2nd LBT unit). Case 5 shows an instance where the basestation has successfully accessed a channel in a basic bandwidth(secondary LBT unit) having the second highest priority and a basicbandwidth (thirdly LBT unit) having the third highest priority, hasfailed to access a channel in a basic bandwidth (primary LBT unit)having the highest priority, and has failed to access a channel in atleast one of the basic bandwidth (thirdly LBT unit) having the thirdhighest priority and a basic bandwidth (fourthly LBT unit) having thefourth highest priority. In case 5, the base station is allowed totransmit a PDSCH through two basic bandwidths (2nd LBT unit and 3rd LBTunit). Case 6 shows an instance where the base station has successfullyaccessed a channel in a basic bandwidth (thirdly LBT unit) having thethird highest priority, and has failed to access a channel in a basicbandwidth (primary LBT unit) having the highest priority, a basicbandwidth (secondary LBT unit) having the second highest priority, and abasic bandwidth (fourthly LBT unit) having the fourth highest priority.In case 6, the base station is allowed to transmit a PDSCH through onebasic bandwidth (3rd LBT unit). Case 7 shows an instance where the basestation has failed to access a channel in a channel in a basic bandwidth(primary LBT unit) having the highest priority and a basic bandwidth(secondary LBT unit) having the second highest priority, and hassuccessfully accessed a channel in the (N−2) number of remaining basicbandwidths (3rd LBT unit, . . . , Nth LBT unit). Number (N−2) is equalto a power of 2. In case 7, the base station is allowed to transmit aPDSCH through (N−2) number of basic bandwidths (3rd LBT unit, . . . ,Nth LBT unit). Case 8 shows an instance where the base station hassuccessfully accessed a channel only in a basic bandwidth (Nth LBT unit)having the lowest priority. In case 8, the base station is allowed totransmit a PDSCH through one basic bandwidth (Nth LBT unit).

FIG. 20 shows an operation in which, when a BWP is configured to includeone or more basic bandwidths according to an embodiment of the presentdisclosure, a base station transmits a PDCCH in a CORESET configured ineach of designated basic bandwidths, according to the prioritiesthereof, and transmits a PDSCH in the BWP.

The base station may divide a BWP into multiple basic bandwidth units,may designate multiple priority basic bandwidths in which a terminalmonitors a PDCCH, and may transmit a PDCCH only in the designatedpriority basic bandwidths. The base station may configure a CORESET ineach of designated basic bandwidths. In another detailed embodiment, thebase station may designate multiple priority basic bandwidths amongbasic bandwidths in which CORESET is configured. In addition, asdescribed above, the bandwidths of CORESET may be configured withinbasic bandwidths, respectively. The terminal may monitor a PDCCH only indesignated priority basic bandwidths.

One or more basic bandwidths in which the base station may transmit aPDCCH may be designated within a BWP. The base station may transmit aPDCCH to the terminal on the basis of a result of channel access in thedesignated basic bandwidths. Specifically, the base station may transmita PDCCH according to the priorities of the designated basic bandwidthson the basis of a result of channel access in the designated basicbandwidths. The base station may transmit a PDCCH in a basic bandwidthhaving the highest priority among basic bandwidths which are designatedbasic bandwidths and in which channel access has been successful. In theembodiments shown in FIG. 20 , the first basic bandwidth (1st LBT unit)and the third basic bandwidth (3rd LBT unit) are designated as basicbandwidths in which a PDCCH may be transmitted. In the embodiments shownin FIG. 20 , when the base station has successfully accessed a channelin the first basic bandwidth (1st LBT unit) and the third basicbandwidth (3rd LBT unit), the base station may transmit a PDCCH in thefirst basic bandwidth (1st LBT unit).

The terminal may monitor a PDCCH in designated basic bandwidths. Theterminal may monitor a PDCCH on the basis of the priorities of thedesignated basic bandwidths. Specifically, the terminal may determinethe sequence of the designated basic bandwidths in which a PDCCH is tobe monitored, on the basis of the priorities of the designated basicbandwidths. For example, when the terminal has failed to receive a PDCCHin a CORESET configured in a bandwidth having the highest priority amongthe designated basic bandwidths, the terminal monitors a PDCCH in adesignated basic bandwidth having the second highest priority. When theterminal receives a PDCCH in one designated basic bandwidth, monitoringa PDCCH in the remaining designated basic bandwidths may be omitted.Specifically, when the terminal receives a PDCCH scheduling a PDCSH inone basic bandwidth, monitoring of a PDCCH scheduling a PDSCH may beomitted in the remaining designated basic bandwidths.

In addition, a PDCCH may schedule a PDCSH transmitted in a basicbandwidth in which the base station has succeeded in channel access. APDCCH may schedule a PDCSH transmitted in basic bandwidths other than atop-priority basic bandwidth, as well as a PDSCH transmitted in thetop-priority basic bandwidth. The base station may transmit a PDCCH in atop-priority basic bandwidth, and the top-priority basic bandwidth is abasic bandwidth having the highest priority among basic bandwidths inwhich the base station has succeeded in channel access therefore, thetop-priority basic bandwidth corresponds to a basic bandwidth having thehighest priority among basic bandwidths, which are designated basicbandwidths and in which the base station has succeeded in channelaccess. The base station may determine a basic bandwidth in which aPDSCH is to be transmitted, on the basis of the top-priority basicbandwidth. The terminal may receive a PDSCH on the basis of PDSCHscheduling information included in a received PDCCH.

In addition, the base station may determine a basic bandwidth in which aPDSCH is to be transmitted, by combining a result of channel access inthe top-priority basic bandwidth, and a result of channel access inother basic bandwidths of a corresponding BWP. In a detailed embodiment,when the base station has also successfully accessed a channel in abasic bandwidth adjacent to the top-priority basic bandwidth, the basestation may transmit a PDSCH on the basis of the top-priority basicbandwidth and the basic bandwidth, in which the base station hassucceeded in channel access and which is adjacent to the top-prioritybasic bandwidth. The base station may transmit a PDSCH through abandwidth having the size of an integer multiple of a basic bandwidth(e.g., 20 MHz*M, wherein M={1, 2, 3, 4, . . . , N}, and N is a naturalnumber). In another detailed embodiment, the base station may transmit aPDSCH through a bandwidth having a size obtained by multiplying a basicbandwidth by a power of 2 (e.g., 20 MHz*2{circumflex over ( )}L, whereinL={0, 1, 2, 3, . . . , X} and X is a natural number). Each of the LBTunits shown in FIG. 20 indicates a basic bandwidth. As described above,in the embodiments shown in FIG. 20 , two basic bandwidths (1st LBT unitand 3rd LBT unit) are designated as basic bandwidths in which a PDCCHmay be transmitted.

FIG. 20 -(a) shows a case where a base station transmits a PDSCH througha bandwidth having the size of an integer multiple of a basic bandwidth.Case 1 shows an instance where the base station has successfullyaccessed a channel in the first basic bandwidth (1st LBT unit), which isa basic bandwidth (primary LBT unit) having the highest priority, andhas failed to access a channel in the second basic bandwidth (2nd LBTunit). In case 1, the base station is allowed to transmit a PDSCHthrough one basic bandwidth (1st LBT unit). Case 2 shows an instancewhere the base station has succeeded in the first basic bandwidth(primary LBT unit), which is a basic bandwidth having the highestpriority, and the second basic bandwidth (2nd LBT unit), and has failedto access a channel in the third basic bandwidth (3rd LBT unit). In case2, the base station is allowed to transmit a PDSCH through two basicbandwidths (1st LBT unit and 2nd LBT unit). Case 3 shows an instancewhere the base station has successfully accessed a channel in the firstbasic bandwidth, which is a basic bandwidth (primary LBT unit) havingthe highest priority, the second basic bandwidth (secondary LBT unit),and the third bandwidth (thirdly LBT unit), and has failed to access achannel in the N-th basic bandwidth (N-th LBT unit). In case 3, the basestation is allowed to transmit a PDSCH through three basic bandwidths(1st LBT unit, 2nd LBT unit, 3rd LBT unit). Case 4 shows an instancewhere the base station has successfully accessed a channel in all (Nnumber of) basic bandwidths. In case 4, the base station is allowed totransmit a PDSCH through N number of basic bandwidths (1st LBT unit, 2ndLBT unit, 3rd LBT unit, . . . Nth LBT unit). The base station transmitsa PDSCH through N number of basic bandwidths (1st LBT unit, 2nd LBTunit, 3rd LBT unit, . . . Nth LBT unit). Case 5 shows an instance wherethe base station has successfully accessed a channel in the third basicbandwidth (3rd LBT unit), which is a basic bandwidth (secondary LBTunit) having the second highest priority, and has failed to access achannel in the first basic bandwidth (1st LBT unit), which is a basicbandwidth (primary LBT unit) having the highest priority, and the N−thbasic bandwidth (N-th LBT unit). In case 5, the base station is allowedto transmit a PDSCH through one basic bandwidth (3rd LBT unit). Case 6shows an instance where the base station has successfully accessed achannel in the third basic bandwidth (3rd LBT unit), which is a basicbandwidth (secondary LBT unit) having the second highest priority, andall the basic bandwidths from the fourth basic bandwidth to the n-thbasic bandwidth, and has failed to access a channel in the first basicbandwidth (1st LBT unit), which is a bandwidth (primary LBT unit) havingthe highest priority. In case 6, the base station is allowed to transmita PDSCH through (N−2) number of basic bandwidths (3rd LBT unit, . . .Nth LBT unit). Case 7 shows an instance where the base station hasfailed to access a channel in basic bandwidths having the first andsecond highest priorities when the n-th basic bandwidth is configured asa basic bandwidth having the third highest priority. In case 7, the basestation is allowed to transmit a PDSCH through one basic bandwidth (NthLBT unit).

FIG. 20 -(b) shows a case where a base station transmits a PDSCH througha bandwidth having a size obtained by multiplying a basic bandwidth by apower of 2. Case 1 shows an instance where the base station hassuccessfully accessed a channel in the first basic bandwidth (1st LBTunit), which is a basic bandwidth (primary LBT unit) having the highestpriority, and has failed to access a channel in the second basicbandwidth (2nd LBT unit). In case 1, the base station is allowed totransmit a PDSCH through one basic bandwidth (1st LBT unit). Case 2shows an instance where the base station has successfully accessed achannel in the first basic bandwidth (1st LBT unit), which is a basicbandwidth (primary LBT unit) having the highest priority, and the secondbasic bandwidth (2nd LBT unit), and has failed to access a channel in atleast one of the third basic bandwidth (3rd LBT unit) and the fourthbasic bandwidth (4th LBT unit). In case 2, the base station is allowedto transmit a PDSCH through two basic bandwidths (1st LBT unit and 2ndLBT unit). Case 3 shows an instance where the base station hassuccessfully accessed a channel in all (N number of) basic bandwidths.In case 3, the base station is allowed to transmit a PDSCH through Nnumber of basic bandwidths. Case 4 shows an instance where the basestation has successfully accessed a channel in the third basic bandwidth(3rd LBT unit), which is a basic bandwidth (secondary LBT unit) havingthe second highest priority, and has failed to access a channel in thefirst basic bandwidth (1st LBT unit), which is a basic bandwidth(primary LBT unit) having the highest priority, and the fourth basicbandwidth (4th LBT unit). In case 4, the base station is allowed totransmit a PDSCH through one basic bandwidth (3rd LBT unit). Case 5shows an instance where the base station has successfully accessed achannel in the third basic bandwidth (3rd LBT unit), which is a basicbandwidth (secondary LBT unit) having the second highest priority, andall the basic bandwidths after the third basic bandwidth (3rd LBT unit),and has failed to access a channel in the first basic bandwidth (1st LBTunit), which is a basic bandwidth (primary LBT unit) having the highestpriority. In case 5, the base station is allowed to transmit a PDSCHthrough (N−2) number of basic bandwidths (3rd LBT unit, . . . Nth LBTunit). Number (N−2) is equal to a power of 2. Case 6 shows an instancewhere the base station has failed to access a channel in a basicbandwidth having the first highest priority and a basic bandwidth havingthe second highest priority when the N-th basic bandwidth is configuredas a basic bandwidth having the third highest priority. In case 6, thebase station is allowed to transmit a PDSCH through one basic bandwidth(N-th LBT unit).

FIG. 21 shows an operation in which, when a BWP is configured to includeone or more basic bandwidths according to an embodiment of the presentdisclosure, one or more basic bandwidths in which a base station maytransmit a PDCCH are designated, and the base station transmits a PDCCHin a CORESET configured in each of the designated basic bandwidths,according to the designated basic bandwidths, and transmits a PDSCH inthe BWP.

One or more basic bandwidths in which the base station may transmit aPDCCH may be designated within a BWP. The base station may transmit aPDCCH to the terminal on the basis of a result of channel access in thedesignated basic bandwidths. The base station may configure a CORESET ineach of the designated basic bandwidths. In another detailed embodiment,the base station may designate one or more basic bandwidths, in which aPDCCH may be transmitted, among basic bandwidths in which CORESETs areconfigured. In addition, as described above, the bandwidths of theCORESETs may be configured within basic bandwidths, respectively.Moreover, all the priorities of designated basic bandwidths for PDCCHtransmission may be same. Specifically, the base station may transmit aPDCCH in one of basic bandwidths which are designated basic bandwidthsand in which channel access has been successful. The base station maydetermine a basic bandwidth in which a PDCCH is to be transmitted, inconsideration of a scheduling algorithm, etc. Moreover, basic bandwidthsin which a PDSCH may be scheduled through a PDCCH of a designated basicbandwidth may not be adjacent to each other and may be disjointed fromeach other. In the embodiment shown in FIG. 21 , the first basicbandwidth (1st LBT unit) and the third basic bandwidth (3rd LBT unit)are designated as basic bandwidths in which a PDCCH may be transmitted.In the embodiment shown in FIG. 21 , when the base station hassuccessfully accessed a channel in the first basic bandwidth (1st LBTunit) and the third basic bandwidth (3rd LBT unit), the base station maytransmit a PDCCH in one of the first basic bandwidth (1st LBT unit) andthe third basic bandwidth (3rd LBT unit).

The terminal may monitor a PDCCH in all designated basic bandwidths.When the terminal has successfully received a PDCCH in one designatedbasic bandwidth, monitoring a PDCCH in the remaining designated basicbandwidths may be omitted. Specifically, when the terminal receives aPDCCH scheduling a PDCSH in one basic bandwidth, monitoring of a PDCCHscheduling a PDSCH may be omitted in the remaining designated basicbandwidths.

In addition, a PDCCH may schedule a PDCSH transmitted in a designatedbasic bandwidth in which the base station has succeeded in channelaccess. A PDCCH may schedule a PDCSH transmitted in basic bandwidthsother than a designated basic bandwidth, as well as a PDCSH transmittedin the designated basic bandwidth. The terminal may receive a PDSCH onthe basis of PDSCH scheduling information included in a received PDCCH.

In addition, the base station may determine a basic bandwidth in which aPDSCH is to be transmitted, by combining a result of channel access inthe designated basic bandwidths, and a result of channel access in otherbasic bandwidths of a corresponding BWP. In a detailed embodiment, whenthe base station has also successfully accessed a channel in a basicbandwidth adjacent to a designated basic bandwidth, the base station maytransmit a PDSCH on the basis of the designated basic bandwidth, and thebasic bandwidth, in which the base station has succeeded in channelaccess and which is adjacent to the designated basic bandwidth. The basestation may transmit a PDSCH through a bandwidth having a size obtainedby multiplying a basic bandwidth by a power of 2 (e.g., 20MHz*2{circumflex over ( )}L, wherein L={0, 1, 2, 3, . . . , X} and X isa natural number). Each of the LBT units shown in FIG. 21 indicates abasic bandwidth. As described above, in the embodiment shown in FIG. 21, two basic bandwidths (1st LBT unit and 3rd LBT unit) are designated asbasic bandwidths in which a PDCCH may be transmitted. In addition, inthe embodiment shown in FIG. 21 , the base station transmits a PDSCHthrough a bandwidth having a size obtained by multiplying a basicbandwidth by a power of 2. Case 1 shows an instance where the basestation has successfully accessed a channel in the first basic bandwidth(1st LBT unit), which is a designated basic bandwidth, and has failed toaccess a channel in the second basic bandwidth (2nd LBT unit). In case1, the base station is allowed to transmit a PDSCH through one basicbandwidth (1st LBT unit). Case 2 shows an instance where the basestation has successfully accessed a channel in the first basic bandwidth(1st LBT unit), which is a designated basic bandwidth, and the secondbasic bandwidth (2nd LBT unit), and has failed to access a channel in atleast one of the third basic bandwidth (3rd LBT unit) and the fourthbasic bandwidth (4th LBT unit). In case 2, the base station is allowedto transmit a PDSCH through two basic bandwidths (1st LBT unit and 2ndLBT unit). Case 3 shows an instance where the base station hassuccessfully accessed a channel in the third basic bandwidth (3rd LBTunit), which is a designated basic bandwidth, and has failed to access achannel in the first basic bandwidth (1st LBT unit), which is adesignated basic bandwidth, and the fourth basic bandwidth (4th LBTunit). In case 3, the base station is allowed to transmit a PDSCHthrough one basic bandwidth (3rd LBT unit). Case 4 shows an instancewhere the base station has successfully accessed a channel in the thirdbasic bandwidth (3rd LBT unit), which is a designated basic bandwidth,and all the basic bandwidths after the third basic bandwidth (3rd LBTunit), and has failed to access a channel in the first basic bandwidth(1st LBT unit), which is a designated basic bandwidth. In case 4, thebase station is allowed to transmit a PDSCH through (N−2) number ofbasic bandwidths (3rd LBT unit, . . . Nth LBT unit). Number (N−2) isequal to a power of 2.

The base station may configure scheduling information of a PDCSH on thebasis of an active BWP. The terminal may determine that an RA field,which is a resource allocation (RA) field of DCI of a PDCCH scheduling aPDSCH, assigns a resource on the basis of an active BWP. The terminalmay receive a PDSCH on the basis of the above determination. The basestation may determine a combination of basic bandwidths transmitting aPDSCH, according to whether there is a channel success in each ofmultiple basic bandwidths included in a BWP, as in the embodimentsdescribed above. Accordingly, the base station is required to make afinal decision on an RA field value of DCI after performing a channelaccess. In addition, the base station is required to make a finaldecision on the size of a resource in which a PDSCH is to betransmitted, after performing a channel access. Accordingly, thecomplexity of an operation in which a base station schedules a PDSCHtransmission and configures a PDCCH may be increased. Therefore, amethod for indicating a resource used for a PDSCH transmission in aPDCCH is required.

The base station may configure an RA field of DCI, to be divided into afirst field indicating a basic bandwidth including a resource assignedfor PDSCH transmission, and a second field indicating the resourceassigned for PDSCH transmission within the basic bandwidth indicated bythe first field. Specifically, the first field may indicate a basicbandwidth index or a combination of basic bandwidth indexes, whichidentifies a basic bandwidth(s) including a resource assigned for PDSCHtransmission. In addition, the base station may configure a value of aRA field of DCI such that the RA field indicates a basic bandwidth indexor a combination of basic bandwidth indexes as well as a resourceassigned for PDSCH transmission within a basic bandwidth(s).Specifically, the terminal may determine a resource assigned for PDSCHtransmission on the basis of the position of a basic bandwidth in whicha PDSCH is transmitted, and a value of an RA field, which are includedin a PDCCH. For example, according to the embodiments shown in FIGS. 19-(a), 20-(a), and 21, when a PDCCH is transmitted in a unit bandwidth(primary LBT unit) having the highest priority, the RA field mayindicate a frequency resource (e.g., case 1, case 2, case 3, and case 4)including a unit bandwidth (primary LBT unit) having the highestpriority. When a PDCCH is transmitted in a unit bandwidth (secondary LBTunit) having the second highest priority, the RA field may indicate afrequency resource (e.g., case 5, case 6, and case 7) including a unitbandwidth (secondary LBT unit) having the second highest priority.

The base station may transmit a PDCCH in one BWP, and schedule a PDSCHtransmitted in a BWP differing from the BWP in which the PDCCH istransmitted, by using the PDCCH. This scheduling is called BWPswitching. In a case where BWP switching occurs as described above, theterminal may require a time for retuning into a BWP in which a PDSCH istransmitted from the base station, in order to receive the PDSCHaccording to BWP switching. Specifically, BWP switching may includecases where the center frequency of a BWP is changed, the frequency bandof a BWP is changed, and the bandwidth of a BWP is changed. According tothe specific situations, the terminal may require a time gap of severalhundred μs. In a case where a PDSCH is transmitted in a licensed band,the base station may schedule a PDSCH transmission securing a time gapdescribed above. However, considering that an apparatus using anunlicensed band like a Wi-Fi apparatus performs CCA in a unit ofintervals, each of which is 9 μs, there is a possibility that anotherwireless communication apparatus uses a frequency resource correspondingto a switched BWP during a time gap occurring at the time of BWPswitching in a case where a PDSCH is transmitted in an unlicensed band.Therefore, at the time of BWP switching, the base station may transmit areservation signal in a changed BWP. Specifically, at the time of BWPswitching, the base station may transmit a reservation signal to afrequency resource in which a PDSCH is to be transmitted, in a changedBWP. In a detailed embodiment, the base station may transmit areservation signal to a frequency resource in which a PDSCH is to betransmitted, in a changed BWP during a time gap for BWP changing on thebasis of a time domain resource allocation (TDRA) of the PDSCH, which isscheduled in the changed BWP at the time of BWP switching. The BWPchanging may include at least one of changing the center frequency of aBWP, changing the frequency band of a BWP, and changing the bandwidth ofa BWP. The base station may generate a reservation signal by extendingthe CP of an OFDM symbol for a PDSCH which the base station is totransmit.

Hereinafter, the present specification provides a downlink controlchannel and data channel reception method and an uplink control channeland data channel transmission method, which allow a bandwidth part(BWP)-based operation in one carrier for NR-U. The present specificationprovides a downlink control channel and data channel reception methodand an uplink control channel and data channel transmission method,which are performed in a BWP configured by one or morelisten-before-talk (LBT) bandwidths existing in one carrier. An exampleof a method proposed in the present specification relates to a methodfor, when a base station performs downlink channel transmission to aterminal in a BWP configured by two or more LBT bandwidths (or LBTsubbands) existing in one carrier, allocating a resource fortransmission of a downlink control channel and a resource fortransmission of a downlink data channel according to a configuration ofan in-carrier guard band, and indicating information relating to theresource allocations. In addition, the method relates to a method bywhich a terminal receives a downlink control channel and a downlink datachannel on a resource assigned from a base station. In addition, amethod proposed in the present specification relates to a method for,when a terminal performs uplink channel transmission to a base station,allocating a resource for transmission of an uplink control channel andan uplink data channel according to a configuration of an in-carrierguard band and indicating information relating to the resourceallocation. In addition, the method relates to a method by which aterminal transmits an uplink control channel and an uplink data channelin a resource scheduled (allocated) from a base station.

FIG. 22 is a diagram illustrating in-carrier guard bands and carrierguard bands in a BWP configured by one or more LBT subbands in awideband carrier according to an embodiment of the presentspecification.

An in-carrier guard band and a carrier guard band according to anembodiment of the present specification will be described with referenceto FIG. 22 . An in-carrier guard band may be a guard band positionedbetween predetermined bandwidths according to a pre-configured criteriain one BWP positioned in one carrier. For example, an in-carrier guardband may indicate a guard band positioned at 20 MHz intervals in one BWPin one carrier having a bandwidth of 80 MHz. A carrier guard band mayindicate a guard band positioned at both ends of a wideband carrier. Acarrier guard band may be configured to be unable to be allocated as aresource for channel transmission. Meanwhile, an in-carrier guard bandmay be configured to be allocated as a resource for channeltransmission. If a base station allocates an in-carrier guard band as aresource for channel transmission, the base station is required tonotify a terminal that the resource is available for channeltransmission. A channel described in the present specification may havea meaning including a control channel and a data channel, and a channeltransmission may have the same meaning as that of a data transmission.

FIG. 23 is a diagram illustrating the number of physical resource blocks(PRBs) which may be continuously used in a BWP having a bandwidth of 20MHz, 40 MHz, or 80 MHz according to an embodiment of the presentspecification.

FIG. 24 is a diagram illustrating the number of physical RBs which maybe used as an in-carrier guard band in a BWP having a bandwidth of 20MHz, 40 MHz, or 80 MHz according to an embodiment of the presentspecification.

Referring to FIG. 24 , in a BWP having a bandwidth of 20 MHz, onesubband may be configured by 51 PRBs. In a BWP having a bandwidth of 40MHz, one subband may be configured by 50 PRBs, and an in-carrier guardband between two adjacent subbands may be configured by six PRBs. In aBWP having a bandwidth of 80 MHz, one subband may be configured by 49 or50 PRBs, and an in-carrier guard band between two adjacent subbands maybe configured by six or seven PRBs.

Referring to FIG. 23 , the number of subbands that are consecutivelyusable in a BWP having a bandwidth of 20 MHz is one, and 51 PRBs may beused as the subband. The number of subbands that are consecutivelyusable in a BWP having a bandwidth of 40 MHz is two, and 106 (50+6+50,see FIG. 24 ) PRBs may be used as each of the subbands. The number ofsubbands that are consecutively usable in a BWP having a bandwidth of 80MHz is four, and 217 (50+6+49+7+49+6+50, see FIG. 24 ) PRBs may be usedas each of the subbands.

In addition, FIG. 24 is a diagram illustrating the number of physicalRBs which may be used for each LBT subband in a BWP having a bandwidthof 20 MHz, 40 MHz, or 80 MHz according to an embodiment of the presentspecification. An intra-carrier guard illustrated in FIG. 24 may havethe same meaning as that an in-carrier guard band described above.

When a downlink control channel is received, a terminal may be unable torecognize whether an in-carrier guard band has been allocated as aresource for transmission of the control channel from a base station.Meanwhile, the terminal may receive, by using a bitmap, an indication ofan LBT (available LBT) subband which is available for channeltransmission, through a group-common (GC)-PDCCH from the base station.However, the terminal is unable to determine whether an in-carrier guardband has been allocated as a resource for transmission of a controlchannel and a data channel, before the terminal receives an indicationof an available LBT subband through a GC-PDCCH from the base station.Therefore, in a case where the base station is to transmit a downlinkcontrol channel, that is, a PDCCH to the terminal, the base station mayallow the terminal to configure a control resource set (CORESET) in aresource except for an in-carrier guard band. The base station maytransmit a PDCCH to the terminal on the CORESET resource. That is, aCORESET may be assigned in an available LBT subband, and in addition,may be assigned to a frequency resource except for an in-carrier guardband in the available LBT subband. The base station may configure theterminal to monitor a PDCCH on a CORESET configured by a resource exceptfor an in-carrier guard band. The terminal may monitor a PDCCH on aCORESET resource configured by a resource except for an in-carrier guardband, configured by the base station, and may perform blind detection ofa PDCCH.

Meanwhile, the base station may indicate, to the terminal, an availableLBT subband through a GC-PDCCH at a time point rather than a DL burststarting time point by using a bitmap. If the terminal receives aGC-PDCCH, there may be no ambiguity between the terminal and the basestation, relating to whether an in-carrier guard band is allocated as aresource for channel transmission. However, in a case where, althoughthe base station indicates the availability of consecutive LBT subbandsfor channel transmission through a GC-PDCCH, the terminal has failed thedetection of the GC-PDCCH, the terminal is unable to know whether anin-carrier guard band is available as a resource for channeltransmission. Therefore, even if the base station configures anin-carrier guard band to be available as a resource for channeltransmission through a GC-PDCCH, the terminal may fail to recognize theconfiguration. Therefore, there may be ambiguity between the terminaland the base station, relating to a resource allocation for anin-carrier guard band (whether the in-carrier guard band is used forchannel transmission).

In other words, the base station may consider whether an in-carrierguard band may be used for channel transmission, and allocate a resource(e.g. a CORESET) for channel transmission, which allows the terminal tomonitor a PDCCH. That is, when an in-carrier guard band is not allowedto be used for channel transmission, a resource for channel transmissionmay be configured on a subband within a BWP, which is identified by anin-carrier guard band. Then, the base station may instruct the terminalto perform PDCCH monitoring for receiving a PDCCH, in the resource forchannel transmission. Then, the base station may transmit a PDCCHthrough the resource for channel transmission. Thereafter, the terminalmay perform blind detection of a PDCCH in the resource for channeltransmission. The base station may transmit, to the terminal,information relating to whether an in-carrier guard band has beenallocated as a resource for channel transmission by considering anin-carrier guard band to be available as a resource for channeltransmission. Then, the base station may indicate whether each ofsubbands in a BWP, which are identified by an in-carrier guard band, isused for downlink channel transmission. The information relating towhether an in-carrier guard band has been allocated as a resource forchannel transmission by considering an in-carrier guard band to beavailable as a resource for channel transmission, and whether each ofsubbands is used for downlink channel transmission may be indicated by abitmap type.

Therefore, the present specification proposes a method for indicating,by a base station, whether an in-carrier guard band is available as aresource for channel transmission. Specifically, the presentspecification proposes a method for indicating through downlink controlinformation (DCI) signaling, which is a dynamic scheduling method.

In a case of downlink transmission, a base station may perform a channelaccess in units of LBT bandwidths in a BWP configured by two or more LBTbandwidths (or LBT subbands). According to whether an in-carrier guardband is available as a resource for channel transmission, whetherconsecutive LBT subbands in a BWP are available for channel transmissionmay be determined. Therefore, when the base station succeeds in achannel access, the base station is required to indicate, to a terminal,whether a resource allocation has been performed by considering anin-carrier guard band to be available as a resource for channeltransmission, or a resource allocation has been performed by consideringan in-carrier guard band to be unavailable as a resource for channeltransmission.

The terminal may receive frequency domain resource allocation (FDRA)information through DCI from the base station. However, the terminal isunable to know a result of a channel access performed by the basestation in a downlink BWP configured by two or more LBT bandwidths (orLBT subbands), which is configured by the base station for the terminal.Therefore, when consecutive LBT subbands in a BWP are available forchannel transmission, the terminal is unable to know whether the basestation has performed a downlink resource allocation by considering anin-carrier guard band to be available as a resource for channeltransmission, or has performed a resource allocation for downlinktransmission on the basis of a resource except for an in-carrier guardband. Therefore, the base station may transmit, to the terminal,signaling indicating whether a resource allocation for downlinktransmission has been performed by considering an in-carrier guard bandto be available as a resource for channel transmission. When thesignaling is received by the terminal, there may be no ambiguityrelating to whether an in-carrier guard band is allocated as a resourcefor channel transmission, when a frequency resource is allocated for adownlink transmission between the terminal and the base station. Theterminal may receive a PDSCH, from the base station, on the basis offrequency domain resource allocation information for downlinktransmission, which is transmitted through DCI.

When the base station performs a resource allocation to the terminal fora downlink channel transmission, the base station is required toindicate whether the resource allocation has been performed byconsidering an in-carrier guard band to be available as a resource forchannel transmission, or the resource allocation has been performed byconsidering an in-carrier guard band to be unavailable as a resource forchannel transmission. The indication method may be as follows.

(Method 1)

Method 1 is a method for performing, by a base station to a terminal andthrough an RRC configuration, signaling relating to whether anin-carrier guard band is able to be allocated as a resource for channeltransmission.

An in-carrier guard band may be configured to be unallocable as aresource for data channel transmission, through an RRC configuration.The base station may allocate a frequency resource except for anin-carrier guard band as a resource for a data channel. The terminal mayassume that a frequency resource except for an in-carrier guard band isallocated for data channel transmission. The terminal may receive a datachannel by interpreting pieces of frequency domain resource allocationinformation for the data channel.

On the contrary, an in-carrier guard band may be configured to beallocable as a resource for channel transmission, through an RRCconfiguration. The base station may determine whether an in-carrierguard band is available as a resource for channel transmission.Specifically, the base station may determine whether to use, as aresource for channel transmission, an RB in which an actual in-carrierguard band is positioned, according to a result of a channel access toconsecutive LBT subbands. Therefore, a method of indicating, by the basestation through DCI, whether an RB in which an actual in-carrier guardband is positioned is used as a resource for channel transmission may beconsidered. That is, the terminal may assume that a frequency resourceincluding an in-carrier guard band is allocable for channeltransmission. Whether an RB in which an actual in-carrier guard band ispositioned is used as a resource for channel transmission may beindicated to the terminal from DCI. The terminal may receive a datachannel by interpreting pieces of frequency domain resource allocationinformation for the data channel through the indicated information.

The above RRC configuration may be commonly applied to both downlinkchannel transmission and uplink channel transmission. Specifically,whether an in-carrier guard band is allocable as a resource for channeltransmission may be configured through an RRC configuration identicallyfor both downlink channel transmission and uplink channel transmission.

On the other hand, a configuration may be applied through independentRRC configurations for downlink channel transmission and uplink channeltransmission. Alternatively, a configuration through an RRCconfiguration may be applied to only downlink channel transmission.

In a case of uplink channel transmission, a resource scheduled for theterminal is a resource allocated to consecutive LBT subbands, and allthe consecutive LBT subbands may succeed in a channel access. Theterminal may perform uplink channel transmission in the scheduledresource allocated to consecutive LBT subbands. If the base stationschedules the resource allocated to consecutive LBT subbands, there isno need to indicate, to the terminal, whether an in-carrier guard bandis allocable as a resource for channel transmission. This is because thebase station may perform a resource allocation for DCI to the terminalby considering whether an in-carrier guard band is used for channeltransmission. Therefore, in a case where the terminal succeeds in achannel access in consecutive LBT subbands, the terminal is expected totransmit an uplink channel to the base station through the scheduledresource of the consecutive LBT subbands including an in-carrier guardband, therefore, there is no ambiguity between the terminal and the basestation, relating to an in-carrier guard band. Therefore, in a case ofuplink transmission, there may be no required RRC configuration thatconfigures whether an in-carrier guard band is allocable as a resourcefor channel transmission.

However, in a case of downlink transmission, even if not all consecutiveLBT subbands succeed in a channel access, a downlink transmission ispossible through a part of the LBT subbands, which has succeeded in thechannel access. Therefore, an RRC configuration indicating whether anin-carrier guard band is allocable as a resource for downlink channeltransmission may be required. Similarly to a case of downlinktransmission, also in a case of uplink channel transmission, if ascheduled resource is a resource allocated to consecutive LBT subbands,and not all the consecutive LBT subbands succeed in a channel access, anuplink channel may be possible in a part of the LBT subbands, which hassucceeded. In this case, even in a case of uplink channel transmission,an RRC configuration indicating whether an in-carrier guard band isallocable as a resource for uplink transmission may be required.

(Method 2)

Method 2 is a method employing dynamic signaling and, particularly, is amethod for signaling, by a base station through DCI, whether anin-carrier guard band is allocable as a resource for channeltransmission.

a) as an explicit signaling method, the base station may indicatewhether an in-carrier guard band is included in a resource for receivinga PDSCH, through a field having one bit included in DCI scheduling aPDSCH. Specifically, the base station may indicate information relatingto that all RBs in which an in-carrier guard band is positioned areincluded in a resource scheduling a PDSCH, through DCI indicatingscheduling of the PDSCH. A terminal may receive the DCI, interpretfrequency domain resource allocation (FDRA) information indicated fromthe DCI, and finally identify frequency domain resource allocationinformation by which a PDSCH is transmitted.

b) as an implicit signaling method, the base station may notify theterminal of frequency domain resource allocation information assignedfor PDSCH transmission according to a result of a channel accessperformed by the base station. Specifically, the base station mayseparately indicate an LBT subband allocated for PDSCH transmission tothe terminal. Alternatively, the base station may transmit frequencydomain resource allocation information jointly coded with DCI includinginformation of an LBT subband. When the base station transmits frequencydomain resource allocation information to the terminal, the terminal maydetermine that the allocation is a resource allocation for consecutiveLBT subbands, by using the information. The terminal may determine thatthe base station has performed a resource allocation for PDSCHtransmission by considering that an in-carrier guard band is availablefor channel transmission. Meanwhile, when the base station transmitsfrequency domain resource allocation information to the terminal, theterminal may determine that the allocation is not a resource allocationfor consecutive LBT subbands, by using the information. When theterminal receives the frequency domain resource allocation informationthrough DCI, the terminal may determine that the base station hasperformed a resource allocation for PDSCH transmission by consideringthat an in-carrier guard band is not available as a resource for channeltransmission.

(Method 3)

A base station may indicate whether an in-carrier guard band isallocable as a resource for channel transmission, through an RRCconfiguration. If an in-carrier guard band is indicated to be allocableas a resource for channel transmission, the base station may include RBsused for an in-carrier guard band on the basis of a BWP configured for aterminal when the base station allocates a resource for downlinktransmission. Whether RBs used for an in-carrier guard band are used fora frequency resource allocation for actual downlink transmission may bedetermined by an FDRA value of DCI. RB indexing is required forallocating a frequency resource for downlink transmission, which may beindicated by an FDRA value of DCI. An RB indexing method may be a methodfor indexing RBs used for an in-carrier guard band lastly, rather than amethod for consecutively indexing RBs including RBs used for anin-carrier guard band. The reason of use of the RB indexing method isthat an FDRA value of DCI may allow the base station to indicate whetheran actual in-carrier guard band is available for channel transmission tothe terminal, and may allow the terminal to determine whether anin-carrier guard band is used when actual resource allocation schedulingis performed. In other words, if the base station fails to successfullyaccess a channel in consecutive LBT subbands even after indicating, tothe terminal through RRC signaling, that an in-carrier guard band isallocable as a resource for channel transmission, an in-carrier guardband is not allowed to be allocated to the terminal. Since the terminalis unable to know whether the base station has succeeded in channelaccess, the terminal is unable to be allocated an in-carrier guard bandin order to prevent the terminal from interpreting FDRA in differentways according to whether the base station has succeeded in channelaccess. For example, as illustrated in two LBT subbands of a 40 MHzcarrier in FIG. 24 , the first LBT subband may be configured by 50 RBs,the second LBT subband may be configured by 50 RBs, and an in-carrierguard band may be configured by six RBs. The 50 RBs included in thefirst LBT subband and the 50 RBs included in the second LBT subband maybe indexed from index number 0 to 99, and the six RBs included in thein-carrier guard band may be indexed from index number 100 to 105. As amethod for allocating a resource for downlink transmission by the basestation, there are two methods including a method for transmitting, to aterminal, the starting position of an RB and the length of the RB byusing a resource indication value (RIV) field of DCI, and allocating aresource for PDSCH transmission, and a method for binding one or moreRBs to configure RB groups (RBGs) and informing of the position of anallocated resource by using a bitmap. In the methods, regardless ofwhether the base station has succeeded in a channel access, the basestation may separately transmit, to the terminal, information (FDRAinformation) relating to that RBs included in an in-carrier guard bandhave been allocated as a resource for PDSCH transmission. The terminalmay receive a PDSCH by commonly interpreting the FDRA informationregardless of whether the base station has succeeded in a channelaccess, by using the indexing method described above.

FIG. 25 is a block diagram showing the configurations of a UE and a basestation according to an embodiment of the present invention. In anembodiment of the present invention, the UE may be implemented withvarious types of wireless communication devices or computing devicesthat are guaranteed to be portable and mobile. The UE may be referred toas a User Equipment (UE), a Station (STA), a Mobile Subscriber (MS), orthe like. In addition, in an embodiment of the present invention, thebase station controls and manages a cell (e.g., a macro cell, a femtocell, a pico cell, etc.) corresponding to a service area, and performsfunctions of a signal transmission, a channel designation, a channelmonitoring, a self diagnosis, a relay, or the like. The base station maybe referred to as next Generation NodeB (gNB) or Access Point (AP).

As shown in the drawing, a UE 100 according to an embodiment of thepresent disclosure may include a processor 110, a communication module120, a memory 130, a user interface 140, and a display unit 150.

First, the processor 110 may execute various instructions or programsand process data within the UE 100. In addition, the processor 110 maycontrol the entire operation including each unit of the UE 100, and maycontrol the transmission/reception of data between the units. Here, theprocessor 110 may be configured to perform an operation according to theembodiments described in the present invention. For example, theprocessor 110 may receive slot configuration information, determine aslot configuration based on the slot configuration information, andperform communication according to the determined slot configuration.

Next, the communication module 120 may be an integrated module thatperforms wireless communication using a wireless communication networkand a wireless LAN access using a wireless LAN. For this, thecommunication module 120 may include a plurality of network interfacecards (NICs) such as cellular communication interface cards 121 and 122and an unlicensed band communication interface card 123 in an internalor external form. In the drawing, the communication module 120 is shownas an integral integration module, but unlike the drawing, each networkinterface card may be independently arranged according to a circuitconfiguration or usage.

The cellular communication interface card 121 may transmit or receive aradio signal with at least one of the base station 200, an externaldevice, and a server by using a mobile communication network and providea cellular communication service in a first frequency band based on theinstructions from the processor 110. According to an embodiment, thecellular communication interface card 121 may include at least one NICmodule using a frequency band of less than 6 GHz. At least one NICmodule of the cellular communication interface card 121 mayindependently perform cellular communication with at least one of thebase station 200, an external device, and a server in accordance withcellular communication standards or protocols in the frequency bandsbelow 6 GHz supported by the corresponding NIC module.

The cellular communication interface card 122 may transmit or receive aradio signal with at least one of the base station 200, an externaldevice, and a server by using a mobile communication network and providea cellular communication service in a second frequency band based on theinstructions from the processor 110. According to an embodiment, thecellular communication interface card 122 may include at least one NICmodule using a frequency band of more than 6 GHz. At least one NICmodule of the cellular communication interface card 122 mayindependently perform cellular communication with at least one of thebase station 200, an external device, and a server in accordance withcellular communication standards or protocols in the frequency bands of6 GHz or more supported by the corresponding NIC module.

The unlicensed band communication interface card 123 transmits orreceives a radio signal with at least one of the base station 200, anexternal device, and a server by using a third frequency band which isan unlicensed band, and provides an unlicensed band communicationservice based on the instructions from the processor 110. The unlicensedband communication interface card 123 may include at least one NICmodule using an unlicensed band. For example, the unlicensed band may bea band of 2.4 GHz or 5 GHz. At least one NIC module of the unlicensedband communication interface card 123 may independently or dependentlyperform wireless communication with at least one of the base station200, an external device, and a server according to the unlicensed bandcommunication standard or protocol of the frequency band supported bythe corresponding NIC module.

The memory 130 stores a control program used in the UE 100 and variouskinds of data therefor. Such a control program may include a prescribedprogram required for performing wireless communication with at least oneamong the base station 200, an external device, and a server.

Next, the user interface 140 includes various kinds of input/outputmeans provided in the UE 100. In other words, the user interface 140 mayreceive a user input using various input means, and the processor 110may control the UE 100 based on the received user input. In addition,the user interface 140 may perform an output based on instructions fromthe processor 110 using various kinds of output means.

Next, the display unit 150 outputs various images on a display screen.The display unit 150 may output various display objects such as contentexecuted by the processor 110 or a user interface based on controlinstructions from the processor 110.

In addition, the base station 200 according to an embodiment of thepresent invention may include a processor 210, a communication module220, and a memory 230.

First, the processor 210 may execute various instructions or programs,and process internal data of the base station 200. In addition, theprocessor 210 may control the entire operations of units in the basestation 200, and control data transmission and reception between theunits. Here, the processor 210 may be configured to perform operationsaccording to embodiments described in the present invention. Forexample, the processor 210 may signal slot configuration and performcommunication according to the signaled slot configuration.

Next, the communication module 220 may be an integrated module thatperforms wireless communication using a wireless communication networkand a wireless LAN access using a wireless LAN. For this, thecommunication module 220 may include a plurality of network interfacecards such as cellular communication interface cards 221 and 222 and anunlicensed band communication interface card 223 in an internal orexternal form. In the drawing, the communication module 220 is shown asan integral integration module, but unlike the drawing, each networkinterface card can be independently arranged according to a circuitconfiguration or usage.

The cellular communication interface card 221 may transmit or receive aradio signal with at least one of the UE 100, an external device, and aserver by using a mobile communication network and provide a cellularcommunication service in the first frequency band based on theinstructions from the processor 210. According to an embodiment, thecellular communication interface card 221 may include at least one NICmodule using a frequency band of less than 6 GHz. The at least one NICmodule of the cellular communication interface card 221 mayindependently perform cellular communication with at least one of the UE100, an external device, and a server in accordance with the cellularcommunication standards or protocols in the frequency bands less than 6GHz supported by the corresponding NIC module.

The cellular communication interface card 222 may transmit or receive aradio signal with at least one of the UE 100, an external device, and aserver by using a mobile communication network and provide a cellularcommunication service in the second frequency band based on theinstructions from the processor 210. According to an embodiment, thecellular communication interface card 222 may include at least one NICmodule using a frequency band of 6 GHz or more. The at least one NICmodule of the cellular communication interface card 222 mayindependently perform cellular communication with at least one of the UE100, an external device, and a server in accordance with the cellularcommunication standards or protocols in the frequency bands 6 GHz ormore supported by the corresponding NIC module.

The unlicensed band communication interface card 223 transmits orreceives a radio signal with at least one of the UE 100, an externaldevice, and a server by using the third frequency band which is anunlicensed band, and provides an unlicensed band communication servicebased on the instructions from the processor 210. The unlicensed bandcommunication interface card 223 may include at least one NIC moduleusing an unlicensed band. For example, the unlicensed band may be a bandof 2.4 GHz or 5 GHz. At least one NIC module of the unlicensed bandcommunication interface card 223 may independently or dependentlyperform wireless communication with at least one of the UE 100, anexternal device, and a server according to the unlicensed bandcommunication standards or protocols of the frequency band supported bythe corresponding NIC module.

FIG. 25 is a block diagram illustrating the UE 100 and the base station200 according to an embodiment of the present invention, and blocksseparately shown are logically divided elements of a device.Accordingly, the aforementioned elements of the device may be mounted ina single chip or a plurality of chips according to the design of thedevice. In addition, a part of the configuration of the UE 100, forexample, a user interface 140, a display unit 150 and the like may beselectively provided in the UE 100. In addition, the user interface 140,the display unit 150 and the like may be additionally provided in thebase station 200, if necessary.

The above embodiments of the present disclosure may be implementedthrough various means. For example, embodiments of the presentdisclosure may be implemented by hardware, firmware, software, or acombination thereof.

In a case of an implementation by hardware, a method according toembodiments of the present disclosure may be implemented by one or moreof application specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), a processor, a controller, a micro controller, and a microprocessor.

In a case of an implementation by firmware or software, a methodaccording to embodiments of the present disclosure may be implemented ina type of a module, a procedure, or a function for performing thefunctions or operations described above. A software code may be storedin a memory and operated by a processor. The memory may be disposedinside or outside the processor, and may exchange data with theprocessor by previously known various means.

FIG. 26 is a flowchart of a method for receiving a downlink channel by aterminal according to an embodiment of the present disclosure.

A method by which a terminal receives a downlink channel transmittedfrom a base station, as described with reference to FIGS. 1 to 25 , willbe described with reference to FIG. 26 .

A terminal may receive first information related to a guard band withina first resource region located in one carrier from a base station(S2610).

The terminal may receive, from the base station, second informationrelated to multiple resource sets, each of which identified by the guardband in the first resource region on the basis of the first information(S2620).

The terminal may receive, from the base station, a downlink channel on aresource indicated by the second information to be available for thereception of the downlink channel (S2630).

The multiple resource sets may be configured by resources except for aresource allocated for the guard band on the basis of the firstinformation.

The second information may be information indicating whether each of themultiple resource sets is available for the reception of the downlinkchannel. The first information may be information related to whether theresource allocated for the guard band is available for the reception ofthe downlink channel. Operation S2620 may be performed when the resourceallocated for the guard band is not used for the reception of thedownlink channel according to the first information.

After operation S2610, the terminal may receive, from the base station,a physical downlink control channel (PDCCH) on a part of the multipleresource sets. The second information may be included in downlinkcontrol information (DCI) of the PDCCH.

The DCI may be group-common DCI. In other words, the DCI may be format2_0 DCI.

In addition, after operation S2610, the terminal may receive, from thebase station, information relating to a second resource region that theterminal monitors for the PDCCH reception.

The second resource region may correspond to a part of the multipleresource sets, and the second resource region may include a resource onwhich the PDCCH is received.

The second resource region may include a resource to which a controlresource set (CORESET) is allocated.

The second information may indicate whether each of the multipleresource sets is available for the transmission of the downlink channel,in a bitmap type.

The downlink channel of operation S2630 may be at least one of aphysical downlink control channel (PDCCH) and a physical downlink sharedchannel (PD SCH).

The first information and the information relating to the secondresource region may be transmitted through higher layer signaling (e.g.an RRC configuration).

The terminal that receives a downlink channel from the base station maybe configured by including a transceiver, a processor functionallyconnected to the transceiver, and a memory which stores instructions foroperations executed by the processor and is connected to the processor.

The operations executed by the processor may be the same as thosedescribed with reference to FIG. 26 .

Some embodiments may also be implemented in the form of a recordingmedium including instructions executable by a computer, such as aprogram module executed by a computer. A computer-readable medium may beany available medium that is accessible by a computer, and includes bothvolatile and nonvolatile media, removable and non-removable media.Further, the computer-readable medium may include both computer storagemedia and communication media. The computer storage medium includes bothvolatile and nonvolatile, removable and non-removable media implementedin any method or technology for storage of information such as computerreadable instructions, data structures, program modules or other data.The communication media typically include computer readableinstructions, data structures, other data in a modulated data signalsuch as program modules, or other transmission mechanisms, and includeany information delivery media.

The description of the present invention described above is onlyexemplary, and it will be understood by those skilled in the art towhich the present invention pertains that various modifications andchanges can be made without changing the technical spirit or essentialfeatures of the present invention. Therefore, it should be construedthat the embodiments described above are illustrative and notrestrictive in all respects. For example, each component described as asingle type may be implemented in a distributed manner, and similarly,components described as being distributed may also be implemented in acombined form.

The scope of the present invention is indicated by the attached claimsrather than the detailed description, and it should be construed thatall changes or modifications derived from the meaning and scope of theclaims and their equivalents are included in the scope of the presentinvention.

1-20. (canceled)
 21. A terminal in a wireless communication system, theterminal comprising: a transceiver; a processor functionally connectedto the transceiver, wherein the processor is configured to: receiveinformation related to a guard-band for at least one of an uplinkchannel and a downlink channel, receive a first downlink controlinformation (DCI) including bitmap, wherein each bit of the bitmapindicates whether each of one or more first sub-bands is available forreception of the downlink channel, receive a second DCI includingscheduling information for transmission of the uplink channel, receivethe downlink channel based on the first DCI, transmit the uplink channelbased on the second DCI, wherein the downlink channel is received on afirst resource, wherein the first resource includes at least onesub-band among the one or more first sub-bands indicated to be availablefor reception of the downlink channel, and the first resource does notinclude a resource for a first guard-band allocated based on informationrelated to the guard-band, wherein the uplink channel is transmitted ona second resource, wherein the second resource includes one or moresecond sub-bands and a resource for a second guard-band allocated basedon information related to the guard-band, wherein a guard-band allocatedbased on information related to the guard-band is located betweenadjacent sub-bands in a frequency domain.
 22. The terminal as claimed in21, wherein, when the uplink channel is scheduled to be transmitted ononly one sub-band, the second resource does not include the resource forthe second guard-band allocated based on information related to theguard-band.
 23. The terminal as claimed in 21, wherein the first DCI isgroup-common DCI (GC DCI).
 24. The terminal as claimed in 21, whereinthe one or more first sub-bands are configured through radio resourcecontrol (RRC) signal.
 25. The terminal as claimed in 21, wherein each ofthe one or more first sub-bands is a unit for channel access in anunlicensed band.
 26. A method for use by a user equipment in a wirelesscommunication system, the method comprising: receiving informationrelated to a guard-band for at least one of an uplink channel and adownlink channel; receiving a first downlink control information (DCI)including bitmap, wherein each bit of the bitmap indicates whether eachof one or more first sub-bands is available for reception of thedownlink channel; receiving a second DCI including schedulinginformation for transmission of the uplink channel; receiving thedownlink channel based on the first DCI; transmitting the uplink channelbased on the second DCI, wherein the downlink channel is received on afirst resource, wherein the first resource includes at least onesub-band among the one or more first sub-bands indicated to be availablefor reception of the downlink channel, and the first resource does notinclude a resource for a first guard-band allocated based on informationrelated to the guard-band, wherein the uplink channel is transmitted ona second resource, wherein the second resource includes one or moresecond sub-bands and a resource for a second guard-band allocated basedon information related to the guard-band, wherein a guard-band allocatedbased on information related to the guard-band is located betweenadjacent sub-bands in a frequency domain.
 27. The method as claimed in26, wherein, when the uplink channel is scheduled to be transmitted ononly one sub-band, the second resource does not include the resource forthe second guard-band allocated based on information related to theguard-band.
 28. The method as claimed in 26, wherein the first DCI isgroup-common DCI (GC DCI).
 29. The method as claimed in 26, wherein theone or more first sub-bands are configured through radio resourcecontrol (RRC) signal.
 30. The method as claimed in 26, wherein each ofthe one or more first sub-bands is a unit for channel access in anunlicensed band.
 31. A method performed by a base station in a wirelesscommunication system, the method comprising: transmitting informationrelated to a guard-band for at least one of an uplink channel and adownlink channel; transmitting a first downlink control information(DCI) including bitmap, wherein each bit of the bitmap indicates whethereach of one or more first sub-bands is available for transmission of thedownlink channel; transmitting a second DCI including schedulinginformation for reception of the uplink channel; transmitting thedownlink channel based on the first DCI; receiving the uplink channelbased on the second DCI, wherein the downlink channel is transmitted ona first resource, wherein the first resource includes at least onesub-band among the one or more first sub-bands indicated to be availablefor transmission of the downlink channel, and the first resource doesnot include a resource for a first guard-band allocated based oninformation related to the guard-band, wherein the uplink channel isreceived on a second resource, wherein the second resource includes oneor more second sub-bands and a resource for a second guard-bandallocated based on information related to the guard-band, wherein aguard-band allocated based on information related to the guard-band islocated between adjacent sub-bands in a frequency domain.
 32. The methodas claimed in 31, wherein, when the uplink channel is scheduled to bereceived on only one sub-band, the second resource does not include theresource for the second guard-band allocated based on informationrelated to the guard-band.
 33. The method as claimed in 31, wherein thefirst DCI is group-common DCI (GC DCI).
 34. The method as claimed in 31,wherein the one or more first sub-bands are configured through radioresource control (RRC) signal.
 35. The method as claimed in 31, whereineach of the one or more first sub-bands is a unit for channel access inan unlicensed band.